All questions
Question 1
Many people think of the Internet as invisible, but it runs on real, physical networks. One central idea is that data travels through layers of hardware. When you send a message, it may go from your phone to a nearby cell tower or Wi-Fi router. Then it moves through cables and switches owned by Internet companies. Much of the world's data even crosses oceans through fiber-optic cables that carry light. These lines must be kept up, guarded from damage, and improved as more people use them.
A second central idea is that speed and reliability depend on choices and limits. The farther data travels, the more delay it can add. Crowded networks can also slow down during busy hours. Companies place servers closer to users in "data centers" so videos and websites load faster. But storms, power outages, or construction accidents can cut off service. That is why networks often build in backup routes.
These two ideas help explain why some places have faster service than others. Areas with fewer cables or older equipment may struggle. Areas with more funding and backup systems can handle heavy use.
Which choice best states a central idea of the passage?
- The Internet is invisible and does not rely on any physical equipment.
- The Internet depends on physical hardware, and that hardware shapes how fast and reliable service is. (correct answer)
- Fiber-optic cables under the ocean carry light signals across the world.
- Data centers exist mainly so that videos and websites can load faster.
Explanation: A central idea is the main point an author develops with supporting details, not a single fact. This passage explains that the Internet runs on physical hardware such as routers, cables, and servers, and that this hardware shapes how fast and reliable service is. Choice B states both parts of that main point, so it best captures a central idea. Choice A is wrong because it claims the Internet has no physical parts, which the passage directly contradicts. Choice C names a true detail about ocean cables but treats it as the whole idea, and Choice D takes one small detail about data centers and treats it as the passage's main point.
Question 2
The passage explains that the brain can change in response to experience. This quality is called neuroplasticity. When a person practices a skill, like playing an instrument, connections between certain brain cells can grow stronger. Over time, the brain becomes better at sending signals along those pathways. This can make the skill easier.
The passage also develops a second central idea. This kind of brain change does not mean it is effortless. Building new pathways usually takes repeated practice and rest. Sleep helps the brain organize information. Taking breaks can also prevent overload. The passage notes that frustration is common. Progress can be slow, especially when a skill is hard.
Finally, the passage explains that neuroplasticity can support recovery after injury. In some cases, therapy helps people practice movements or speech. Then other parts of the brain can take over damaged tasks. Recovery has limits, but the passage stresses that targeted practice can improve function.
Which statement is best classified as a supporting detail rather than a central idea?
- Sleep can help the brain organize information during learning. (correct answer)
- The brain can change in response to experience, strengthening its connections through practice.
- Neuroplasticity can aid learning and can also support recovery after injury through targeted practice.
- Changing the brain usually takes repeated practice and time, rather than happening instantly.
Explanation: A central idea is a big point the whole passage builds, while a supporting detail is one smaller fact that backs it up. That the brain changes with experience, that change takes practice and time, and that it aids recovery are the passage's main ideas. The point about sleep helping the brain organize information is one specific detail under the "change takes effort" idea. Choice A is that detail, so it is correct, while B, C, and D each state a central idea.
Question 3
In the early days of space travel, rockets had one main job: to escape Earth's gravity. Reaching orbit takes enormous speed, and that speed takes huge amounts of fuel. But carrying all that fuel makes a rocket heavy. To solve this, engineers use stages, which are separate sections that drop away once their fuel runs out. Dropping the empty stages lowers the weight during flight and makes reaching orbit easier.
Modern space missions also depend on careful planning after liftoff. Satellites must be placed in the right orbit for their job. A weather satellite may need to pass over many parts of Earth. A communications satellite may need to stay above the same region. Planners work out flight paths, fuel for small changes, and launch timing so each rocket reaches its target.
New technology is changing the cost of space travel too. Some rocket boosters can now return to Earth and fly again. This means engineers do not have to build a brand-new booster for every mission. Together, staging, orbit planning, and reusable parts make space travel more practical.
Which choice best states two central ideas of the passage?
- Rocket stages drop away during flight, and weather satellites pass over many parts of Earth.
- Reaching orbit takes engineering solutions like staging, and missions also rely on orbit planning and reusable parts. (correct answer)
- Space travel has become easy because modern rockets no longer need much fuel to reach orbit.
- The main purpose of every rocket is to keep one communications satellite above a single region.
Explanation: Central ideas are the main points an author builds across a passage, not small details. This passage develops two of them: that reaching orbit requires engineering solutions such as staging, and that successful missions also depend on careful orbit planning and on new ways to lower cost. Choice B states both of these main points. Choice A is wrong because it lists two minor details instead of the central ideas. Choice C is wrong because the passage never says space travel is easy or that fuel no longer matters, and Choice D is wrong because it treats one small detail as if it were the whole passage.
Question 4
Many products travel long distances before they reach a store. Supply chains are the steps that move materials from producers to customers. A single T-shirt, for example, might use cotton grown in one country and fabric made in another. The sewing might happen in a third country, before the shirt is shipped to warehouses.
One central idea is that long supply chains can be efficient, but also fragile. Companies often pick faraway factories because the costs are lower, or because of their special skills and machines. However, problems can delay deliveries everywhere. A storm may close a port, truck drivers may be scarce, or a factory may shut down.
A second central idea is that some businesses are changing how they handle risk. Some now keep extra stock of important parts, use several suppliers instead of just one, or move some work closer to their customers. These choices can raise costs, but they can also lower the chance of empty shelves.
Which choice best explains how the passage develops its central ideas?
- It introduces supply chains with an example, explains the strengths and weaknesses of long chains, and then describes how businesses lower disruption risk. (correct answer)
- It introduces supply chains with an example, argues that faraway factories are always a mistake, and then urges every company to buy only from local suppliers.
- It introduces supply chains with an example, lists the delays that can slow deliveries, and then predicts that empty shelves will soon disappear from stores.
- It introduces supply chains with an example, explains why long chains are fragile, and then claims that lowering costs is the only goal that businesses should have.
Explanation: The passage moves through a clear structure. It first defines supply chains using the T-shirt example, then explains that long chains are efficient but fragile, and finally describes how some businesses lower their risk. The correct choice traces exactly those three steps in order.
The choice that says faraway factories are 'always a mistake' misreads the passage, which explains that companies pick them for good reasons like lower costs and special skills. The choice that predicts empty shelves 'will soon disappear' overstates the passage, which only says risk choices can lower the chance of empty shelves, not end them. The choice that claims lowering costs is 'the only goal' contradicts the passage, which shows businesses accepting higher costs to reduce risk. Only the first choice matches what the passage actually does from beginning to end.
Question 5
When students search online, it can feel as if the first result must be the best. The passage explains that search engines rank pages using many signals. These include how many sites link to a page. They also include how closely the words match the search. These signals can help students find useful information quickly. But they do not guarantee that a page is accurate. A popular page can still contain mistakes. A strong headline can make weak evidence sound convincing.
A second central idea is that readers can take specific steps to judge how trustworthy a page is. The passage suggests checking the author's background. It also suggests looking for dates to see whether the information is current. And it suggests comparing claims across several reliable sources. It recommends reading beyond the first paragraph, to see whether the article gives real evidence, such as data, quotations, or links.
The passage concludes that online research is a skill. Instead of trusting the rankings alone, students should combine an understanding of how results are created with careful checking of sources.
How are the two central ideas developed and connected in the passage?
- The passage first explains how search rankings actually work, then shows how that knowledge leads to steps for judging a page's credibility. (correct answer)
- The passage first describes several steps for checking credibility, then treats the way rankings work as a separate topic that its checking steps do not really depend on.
- The passage first explains how search engines rank pages, then argues that popular pages ranked highly are the ones most likely to be accurate and trustworthy.
- The passage first describes ways to research an author's background, then presents those steps as the only skill that careful online reading actually requires.
Explanation: The passage builds two central ideas in order. First it explains how search engines rank pages using signals like links and word matches. Then it uses that understanding to introduce steps for judging whether a page is trustworthy, showing that knowing how rankings work is why the checking steps matter. The correct answer captures both this order and this connection. One choice reverses that connection, claiming the checking steps stand apart and don't really depend on understanding rankings — but the passage links them directly. Another choice gets the ranking idea right but then twists it, saying popular high-ranked pages are the most accurate, when the passage warns that popular pages can still contain mistakes. The last choice narrows the passage down to only researching an author, treating that single step as the whole skill and ignoring both the ranking idea and the other checking steps the passage lists. Only the correct answer keeps both central ideas and shows how the first develops into the second.
Question 6
During the Great Migration, many African American families moved from the rural South to cities in the North and West. One big reason was money. In the South, many workers were stuck in low-paying farm jobs or unfair sharecropping deals. Northern factories offered work that seemed to pay more steadily, especially during World War I. Another reason was safety and civil rights. In many Southern towns, laws and customs enforced segregation and limited the right to vote. Violence and threats also made daily life dangerous for some families. Letters from relatives and newspapers described Northern cities in a hopeful way. Racism still existed there, but there were sometimes more chances to go to school, join groups, and take part in politics. The move changed both the places people left and the places they entered. Southern towns lost workers. Northern neighborhoods grew fast, which led to crowded housing but also new businesses, churches, and music. Over time, the movement even shaped national politics, as growing city communities pushed for change.
Which choice best states two central ideas of the passage?
- African American families moved north chiefly to find better weather, and factory work in the South had mostly disappeared by the time of World War I.
- African American families migrated for economic and for safety and civil-rights reasons, and the movement changed both Southern and Northern communities over time. (correct answer)
- Letters and newspapers were the only reliable sources families had, and their hopeful descriptions guaranteed that life in Northern cities would be easy and free of racism.
- Crowded city housing became the single most serious problem the country ever faced, and this housing crisis was the only lasting effect the migration left behind.
Explanation: A central idea is a main point the author develops across the passage, not one small detail. This passage builds two: families migrated for economic reasons and for safety and civil rights, and the movement reshaped both the communities they left and the ones they joined. The correct choice names both of these ideas together. The choice about better weather is wrong because the passage never mentions weather and says Northern jobs, not vanished Southern ones, drew families. The choice about letters and newspapers takes a single detail and overstates it, claiming those sources 'guaranteed' an easy, racism-free life—but the passage says racism still existed in the North. The choice about crowded housing turns one effect into an absurd 'single most serious problem the country ever faced' and ignores the passage's other effects, like new businesses, churches, music, and political change. Only one choice captures the passage's two big ideas without distorting the text.
Question 7
In many school cafeterias, food waste is a daily problem. Waste happens for several reasons. Students may have short lunch periods, they may be required to take items they do not want, or they may be unfamiliar with certain foods. When edible food is thrown away, schools lose money and more trash ends up in landfills.
A second central idea is that reducing waste takes changes in routine, not just reminders. Some schools schedule recess before lunch, so students arrive hungry and have more time to eat. Others let students choose their portions or start share tables, where unopened items can be left for classmates. These strategies can cut waste while still following health rules.
There is also the food that cannot be saved. Composting turns scraps into soil for gardens, returning nutrients to the ground instead of sending them to a landfill. Together, prevention, safe sharing, and composting can reduce both waste and costs.
Which choice best states two central ideas of the passage?
- Short lunch periods are the single cause of food waste, and composting is the only method schools can use to deal with leftover scraps.
- Cafeteria food waste has several causes, and reducing it takes practical changes in routine, along with systems like sharing and composting. (correct answer)
- Cafeterias should stop offering fresh food entirely, and students should be reminded more often to finish everything on their trays.
- Composting scraps into garden soil is the passage's main focus, and share tables mostly help schools follow strict health rules.
Explanation: A central idea is a main point the passage develops. This text builds two: that cafeteria waste has several causes, and that cutting it takes real changes in routine plus systems like share tables and composting. The choice naming several causes and practical routine changes with sharing and composting captures both, so it is correct. The option that calls short lunch periods the single cause is wrong because the passage lists several causes and treats composting as one method among prevention and sharing. The option about stopping fresh food and relying on reminders contradicts the text, which says change in routine matters more than reminders. The option treating composting as the main focus overstates one part the passage mentions last, and it misreads share tables as being mainly about health rules rather than reducing waste. Only one choice names both central ideas without twisting or shrinking them.
Question 8
Recycling is often called a simple habit. But it is really part of a larger system for cutting waste. Paper, glass, and some plastics can be collected and reused. Then fewer raw materials have to come from forests, mines, or oil fields. Using fewer raw materials also cuts the pollution made when we dig them up and turn them into goods.
A second central idea is that recycling works best when a community does more than toss items in a bin. People have to sort the materials the right way. Food scraps or mixed materials can ruin a whole batch. Towns and companies also need the right factories to handle the materials. And they need buyers who will turn them into new products.
The passage gives examples to support these ideas. Aluminum, for one, can be recycled again and again. Making aluminum from old cans uses far less energy than making it from raw ore. Recycling works best when personal choices and community systems work together.
Which choice best separates a central idea from a supporting detail in the passage?
- Central idea: aluminum can be recycled again and again. Supporting detail: recycling reduces the need to take new raw materials from the earth.
- Central idea: recycling is part of reducing waste and saving resources. Supporting detail: making aluminum from recycled cans uses far less energy than making it from raw ore. (correct answer)
- Central idea: recycling works best when personal choices and community systems work together. Supporting detail: paper, glass, and some plastics can be collected and reused instead of thrown away.
- Central idea: sorting materials correctly is the only thing that matters in recycling. Supporting detail: contamination from food scraps can ruin a whole batch of recycling at once.
Explanation: A central idea is a big, overall point the passage makes, while a supporting detail is a smaller fact that backs it up. The passage's main point is that recycling helps reduce waste and save resources, and the fact that recycled aluminum takes far less energy is one example that supports it — so that pairing is correct. Another choice flips the two, treating aluminum being recyclable (a detail) as the central idea while calling a real central idea the detail. One choice names a true central idea but then labels another central idea as if it were just a supporting detail, so the two parts do not fit together as a big point and a small fact. The last choice overstates the passage: it says sorting is 'the only thing that matters,' but the passage says communities also need the right factories and buyers, so sorting is important but not the only requirement.
Question 9
Read the passage and answer the question.
When people hear the word “compost,” they often picture a pile of leaves rotting in a corner of a yard. In reality, composting is a controlled process that turns food scraps and yard waste into a dark material that gardeners can mix into soil. One central reason compost matters is that it keeps organic waste out of landfills. In a landfill, food waste is buried without much oxygen, and it can produce methane, a gas that traps heat in the atmosphere.
Compost also helps soil work better. The finished material can improve the soil’s ability to hold water, which is useful during dry weeks. It can also make soil less compact, allowing roots to spread and earthworms to move through the ground. Some communities collect compost in bins the way they collect recycling, then send it to facilities that monitor temperature and moisture so the process breaks down waste efficiently.
Not every item belongs in a compost bin, though. Meat and dairy can attract pests, and certain “compostable” plastics only break down in industrial facilities, not in a backyard pile. Because of these limits, many compost programs teach residents what to include and what to leave out.
Which choice best provides an objective summary of the passage?
- The passage explains what composting is, describes how it can reduce landfill waste and improve soil, and notes that successful composting requires following guidelines about which materials to include. (correct answer)
- The passage argues that everyone should compost because landfills are terrible, and it insists that composting is clearly the only truly responsible choice a household can make about its food waste.
- The passage focuses mainly on describing how communities collect compost in bins and send it to facilities that carefully monitor the temperature and moisture of the waste being broken down.
- The passage centers on explaining why meat, dairy, and certain compostable plastics should be avoided, since these problem materials are the main reason composting programs exist in the first place.
Explanation: An objective summary reports the passage's central ideas factually, without adding opinion and without treating one detail as the whole point. The correct choice does this: it states what composting is, that it can cut landfill waste and improve soil, and that it works best when people follow guidelines about materials—the three main ideas the passage develops.
The choice claiming everyone "should" compost because landfills are "terrible" and composting is the "only responsible choice" adds opinion and judgment the passage never makes, so it is not objective.
The choice about collection bins and monitored facilities is accurate but only a supporting detail from one paragraph; a summary must cover the whole passage, not zoom in on a single fact.
The choice saying the passage centers on avoiding meat, dairy, and certain plastics also mistakes a detail for the main point—those limits appear only at the end, and the passage never claims they are why composting programs exist.
Question 10
Renewable energy is a broad topic. It includes power sources that can be replaced naturally, like sunlight and wind. The passage explains one central idea. Compared to burning coal or oil, wind turbines and solar panels make electricity with far fewer greenhouse gases. This happens while they run. Because these technologies do not burn fuel each day, they can cut the air pollution that adds to climate change and smog.
A second central idea is that the costs of renewable energy are complicated. Building a wind farm or installing solar panels can take high upfront spending for equipment, permits, and construction. However, once the system is running, the fuel is free, and upkeep costs can be steady. Over many years, this can make the total cost close to that of fossil-fuel plants. This is especially true when fuel prices rise.
The passage adds that communities also have to plan for the challenges. Solar panels do not make electricity at night, and wind speeds change. So energy storage and updated power grids can help balance supply and demand. The passage concludes that understanding both the benefits and the costs helps leaders. They can then choose energy mixes that fit local needs.
Which choice correctly identifies the topic and a central idea from the passage?
- Topic: solar panels; Central idea: the passage focuses only on how solar panels are cheaper to install than any other kind of power source.
- Topic: renewable energy; Central idea: renewable sources can reduce greenhouse gas emissions compared to fossil fuels. (correct answer)
- Topic: climate change; Central idea: the passage argues that stopping climate change is the one goal driving every energy decision leaders make.
- Topic: electricity costs; Central idea: the high upfront spending on a wind farm always makes renewable energy far pricier than fossil-fuel plants.
Explanation: The topic is the broad subject the whole passage covers, and a central idea is a main point the passage makes about it. The passage as a whole is about renewable energy, and one of its clearly stated main points is that renewable sources produce fewer greenhouse gases than fossil fuels—so the choice naming renewable energy and lower emissions is correct. Naming solar panels as the topic is too narrow, since solar is only one example, and the passage never claims solar is the cheapest option. Naming climate change as the topic mistakes a detail for the whole subject; the passage treats climate change as one benefit to weigh, not the single goal behind every decision. Naming electricity costs shrinks the broad topic, and its claim ignores the passage's point that over many years renewable costs can come close to fossil-fuel costs, especially when fuel prices rise. Only one choice matches both the passage's true topic and one of its actual central ideas.
Question 11
Coral reefs may look like colorful rocks, but they are living communities built by tiny animals called coral polyps. When ocean water stays warm for a long time, corals can get stressed and push out the algae that live inside them. The algae give the coral much of its food and color, so the reef turns pale. This is a process called bleaching. If cooler water returns quickly, corals may recover. But repeated heat stress can weaken or kill large sections of a reef.
The passage also explains why reefs matter to people. Reefs give shelter to many fish and other sea life, which supports fishing jobs and local diets. Their complex shapes can reduce the energy of waves, helping protect shorelines during storms. In some places, reef tourism brings money to communities through snorkeling and diving.
Scientists and local groups are testing different responses. Some efforts focus on cutting the pollution that makes corals weaker, such as runoff that carries fertilizer. Other projects grow corals in nurseries and move them to damaged areas. These steps can help. But the passage notes that long-term reef health depends on limiting the ocean warming that triggers bleaching.
How is the central idea that warming oceans harm coral reefs developed across the passage?
- By describing why reefs matter to people, explaining that they support fishing and tourism, and concluding that protecting them mainly requires reducing ocean pollution.
- By explaining the bleaching process, describing what happens when heat stress repeats, and tying those effects to the need to limit ocean warming. (correct answer)
- By showing how corals lose their color, explaining that damaged reefs always recover on their own, and stating that human action makes little difference to reef health.
- By focusing on how coral nurseries are built and how corals are moved, while treating ocean temperature as an issue that does not really affect reefs.
Explanation: To see how a central idea is developed, trace the steps the passage takes. It first explains bleaching, then describes what repeated heat stress does to a reef, and finally links those effects to the need to limit ocean warming. The choice that follows that build is correct. The option about reefs mattering to people picks a supporting section and names pollution as the main fix, but the passage says long-term health depends on limiting warming, not mainly on pollution. The option claiming damaged reefs always recover and that human action barely matters contradicts the passage, which says repeated heat stress can kill reefs and that limiting warming matters. The option about nurseries covers only one response effort and wrongly dismisses ocean temperature, which the passage names as the trigger for bleaching. Only one choice traces the full path from cause to effect to solution.
Question 12
In the late 1800s and early 1900s, many Americans moved from farms to cities to take factory jobs. This shift changed the way people worked. In factories, a worker often did one task over and over instead of making a whole product. This system made more goods, faster. But it could also be tiring and dangerous, especially when machines had no safety guards.
These conditions helped lead to labor organizing. As factories grew, workers saw that one person complaining to a boss rarely changed anything. So groups of workers formed unions to push for shorter hours, safer workplaces, and better pay. Strikes could stop production and put pressure on owners. At times, though, strikes also led to conflict with police or with workers hired to replace them.
New laws and public attention slowly changed some conditions. Reports about child labor and injuries convinced some lawmakers to set age limits and require safer equipment. The problems did not disappear. Still, changes in work, group action, and government all shaped one another.
Which choice best summarizes the passage objectively?
- Factory work raised production but created harsh conditions, and workers and lawmakers responded with unions and new laws. (correct answer)
- Factory work raised production but created harsh conditions, and courageous unions bravely forced greedy owners to finally treat workers fairly.
- Factory work raised production, and the passage mainly explains how the new machines worked and why city life beat farm life.
- Factory work raised production but created harsh conditions, and new laws quickly ended child labor and solved every safety problem for good.
Explanation: An objective summary states a text's main points fairly, without adding opinions or overstating what is said. This passage makes two connected points: factory work increased production but created harsh conditions, and workers and lawmakers responded with unions and new laws. The best answer captures both points in neutral language. The choice about "courageous" unions and "greedy" owners is wrong because it uses loaded, one-sided wording that adds opinion the text never states. The choice claiming the passage explains how machines worked and that city life "beat" farm life names a focus the passage does not have and adds a judgment it never makes. The choice saying laws "quickly ended child labor and solved every safety problem" overstates the results, which the passage denies when it says "The problems did not disappear."
Question 13
Many people think of microbes only as germs. But microbes also play helpful roles in the human body. In the gut, communities of bacteria help break down certain foods and even make vitamins. Scientists have found that different diets can change which microbes grow well. That, in turn, may affect how well the body uses nutrients.
A second central idea is that the balance of microbes can shape health in more than one way. Research suggests that some microbes help train the immune system to spot harmful invaders. Sometimes that balance is thrown off, for example after a strong course of antibiotics. Then some people have stomach problems, because helpful bacteria were reduced along with the harmful ones.
Researchers are still learning, so simple answers are rare. Probiotic foods and supplements may help some people. But results vary, and medical advice matters for serious conditions.
Which statement best identifies the topic and a central idea of the passage?
- Topic: vitamins made in the gut. Central idea: the vitamins produced by gut bacteria are the passage's main concern, and everything else it mentions is only background detail.
- Topic: antibiotics and the gut. Central idea: antibiotics may disrupt the microbe balance, which the passage presents as its single most important point about health.
- Topic: microbes in the human body. Central idea: helpful microbes support digestion and can affect health by interacting with diet and the immune system. (correct answer)
- Topic: the immune system and microbes. Central idea: the immune system on its own is the passage's central focus, and the discussion of digestion serves mainly to introduce it.
Explanation: The topic is what the whole passage is about, and a central idea is a main point it makes about that topic. The passage discusses microbes in the human body, and its main point is that helpful microbes support digestion and can affect health through both diet and the immune system. The choice naming microbes in the human body captures the full topic and both central ideas the passage develops. The vitamins choice narrows the topic to just one detail the passage mentions in passing, so it misses the broader focus. The antibiotics choice treats one supporting example as if it were the passage's single main point, ignoring digestion and the immune system. The immune-system choice also shrinks the passage to one part and wrongly claims digestion is only there to introduce it, when digestion is developed as a central idea in its own right. Only one choice names the whole topic and the passage's actual main points.
Question 14
In the early 1900s, many American cities were crowded and unhealthy. Trash often piled up in streets, and open sewers spread disease. Reformers led a "public health movement." They pushed for cleaner water, better waste removal, and rules for housing. Over time, cities built water-treatment plants. They also set up systems to collect garbage more regularly.
These changes were not only about cleanliness. They were also about preventing illness. Cities began to filter and clean their drinking water. After that, deaths from diseases like typhoid dropped sharply. Health departments began tracking outbreaks. This helped officials respond faster when problems appeared.
However, progress was uneven. Some neighborhoods received new services sooner than others. This often happened because richer areas had more power in city hall. Building modern systems also cost money. So leaders argued over taxes and budgets. Even so, public health reforms changed city life. They made basic services more reliable for many residents. This included safe water and regular trash collection.
Which choice is a central idea of the passage, not just a supporting detail?
- Cities built water-treatment plants and improved waste removal to reduce disease and improve health. (correct answer)
- Cleaner drinking water led to sharp drops in deaths from diseases such as typhoid over time.
- City leaders often argued over the taxes and budgets needed to pay for new public systems.
- Piled-up trash and open sewers spread disease in crowded cities during the early 1900s.
Explanation: A central idea sums up what the whole passage is about, not one fact from it. The passage returns again and again to how cities improved their water and waste systems in order to fight disease and protect people's health, which is exactly the point that cities built water-treatment plants and improved waste removal to reduce disease and improve health. The choice about cleaner water lowering typhoid deaths is true, but it names one result of those changes rather than the passage's overall message. The choice about leaders arguing over taxes and budgets is only a detail explaining why progress was uneven, not the main idea. The choice about trash and sewers spreading disease describes the early problem the reforms were meant to fix, so it is background, not the central point. Only the first choice covers the passage as a whole.
Question 15
In some schools, students use block scheduling. In this system, classes meet for longer periods but fewer times each week. One central idea about block scheduling is that longer class time can support certain kinds of learning. Teachers may have time for labs, debates, writing workshops, or projects that are hard to finish in a short period. Students can also spend more time practicing a skill while the instructions are still fresh.
A second central idea is that the same schedule can create new challenges. If a student misses a day, they miss a larger chunk of instruction. Some students find it harder to stay focused for a long class, especially if lessons rely only on lecture. Also, a course that meets for only one semester may end months before a final exam. Students may then need review to remember the material.
Because of these trade-offs, schools often adjust block scheduling rather than using one strict model. Some add short support periods. Others alternate days to balance focus and flexibility.
Which choice best provides an objective summary of the passage?
- The passage describes block scheduling, noting that longer periods allow deeper activities but also create challenges like missed instruction and focus problems, and that schools adjust the model to manage trade-offs. (correct answer)
- The passage focuses on the benefits of longer class periods, explaining how they give teachers time for labs and projects, and it suggests that most schools should adopt this schedule for stronger learning.
- The passage mainly lists activities that fill a long class period, such as debates, labs, and writing workshops, and it treats these as the central point rather than the scheduling system itself.
- The passage explains why missing school is a serious problem, arguing that students lose a large chunk of instruction and should try much harder to attend every scheduled class.
Explanation: An objective summary fairly states all the main points without adding an opinion. The passage presents two central ideas—that longer periods can support deeper learning and that they also create challenges—and it ends by noting that schools adjust the model. The choice that captures the benefits, the challenges, and those adjustments is the best summary. The choice about the benefits of longer periods is only partly right: it covers the advantages but drops the challenges, and it adds the opinion that most schools should adopt the schedule, which the passage never says. The choice about activities mistakes the examples (labs, debates, workshops) for the main point, when they are only support for one central idea. The choice about missing school seizes on a single detail and turns it into the passage's argument, ignoring everything else. Only the full, balanced summary fits what an objective summary must do.
Question 16
Some farmers plant cover crops, such as clover, rye, or radishes, not to harvest them, but to improve the soil between main crops. One central idea is that cover crops can protect and rebuild soil. Their roots hold soil in place during heavy rain, which reduces erosion. When the plants are later cut and left to break down, they add organic matter that can improve the soil's structure.
Another central idea is that cover crops affect farm economics and management. Buying seed and planting an extra crop costs money and time. Farmers also have to decide when to plant the cover crop and when to end it, so it does not compete with the main crop for water. Yet cover crops can save money in other ways. Some types, like legumes, add nitrogen to the soil, which can lower the need for fertilizer. Better soil can also soak up water more easily, which may help fields handle drought or sudden storms.
The passage shows that cover crops are not a simple, free solution. Instead, they offer real environmental benefits while requiring careful planning to fit each farm's budget and climate.
Which choice best states two central ideas of the passage?
- Cover crops protect the soil by holding it in place during rain, and they are the cheapest option available to nearly every farmer looking to raise a main crop.
- Cover crops improve soil by reducing erosion and adding organic matter, and they bring economic and management trade-offs that can create both costs and savings. (correct answer)
- Cover crops build healthier soil over time, and the main point is that farmers should always plant legumes because they add nitrogen and remove any need for fertilizer.
- Cover crops require money and careful timing to manage, and the passage's real point is that soil erosion is now the single biggest problem facing farms everywhere.
Explanation: A central idea is a main point the author develops across the passage, not one detail stretched too far. This passage builds two ideas together: cover crops protect and rebuild soil, and they bring trade-offs in cost and management. The answer naming both erosion-and-organic-matter and the cost-and-savings trade-offs captures both, so it is best. The choice calling cover crops the cheapest option gets one idea right but adds a claim the passage denies—it says they are 'not a simple, free solution.' The choice about always planting legumes twists a small detail into a rule the author never states and ignores the trade-offs entirely. The choice ending with erosion as 'the single biggest problem facing farms everywhere' overstates one detail and drops the soil-rebuilding and economic ideas, so it names only part of the passage. Only the correct choice states both central ideas without exaggeration.
Question 17
In many cities, summer nights are getting warmer faster than nearby rural areas. One reason is the urban heat island effect. Dark roofs and roads soak up sunlight during the day. They release that heat slowly after sunset, which keeps neighborhoods warmer. Tall buildings can also block the wind that would otherwise carry heat away. Scientists measure this by comparing temperatures from weather stations downtown and in parks or farmland outside the city.
City planners are not stuck just noticing the problem. They can reduce it. Planting more trees adds shade and cools the air as water evaporates from leaves. Some cities replace black asphalt with lighter pavement that reflects more sunlight. They also encourage cool roofs made from reflective materials. These changes can lower local temperatures and reduce the need for air conditioning.
The passage also explains why this matters for health and budgets. Hotter nights make it harder for bodies to recover from daytime heat. This raises the risk of heat illness, especially for older adults and people without good cooling. Higher air conditioning use can raise electric bills and strain power grids during heat waves. By combining temperature data with design changes, cities can protect residents and manage energy demand.
Which option best states two central ideas of the passage?
- Cities have taller buildings than the countryside, and the way wind moves through downtown streets is somewhat different from open land.
- Sunlight strikes city neighborhoods far more strongly than it strikes rural areas, and that stronger sunlight is what makes urban nights so warm.
- The passage lays out the reasons certain neighborhoods stay warmer and shows how thoughtful design choices can protect people and save energy. (correct answer)
- Running air conditioners is the single biggest reason downtown areas stay warm at night, and overloaded power grids simply cannot cope during heat waves.
Explanation: A central idea is a passage's biggest overall point, not one small fact. The correct choice captures both large points the passage builds: the reasons some neighborhoods stay warmer and the design changes that protect people and lower energy use. The choice about taller buildings and wind names only tiny details from the first paragraph, so it misses the passage's true main ideas. The choice claiming sunlight strikes cities more strongly misreads the text, which says dark surfaces absorb and slowly release heat, not that the sun itself shines harder on cities. The choice blaming air conditioning as the single biggest cause of warmth also misreads the passage, which lists air conditioning only as something that adds to demand during heat waves, never as the reason cities stay warm. Only one choice states two ideas that are both large and both actually supported by the whole passage.
Question 18
When a new disease appears, public health workers try to understand how it spreads. Contact tracing is one tool for slowing outbreaks. If a person tests positive, trained workers ask where that person has been and who they were near. Those contacts can then be notified and tested. They are advised to stay home so the illness does not spread further.
The passage develops a second idea. Contact tracing depends on trust and good communication. People may hesitate to share information if they fear blame or job loss. To improve cooperation, health departments may protect privacy and give clear explanations. They may also connect people with resources like food delivery or temporary housing, so they can isolate safely.
The passage also notes some limits. Contact tracing works best when case numbers are low and testing is quick. During very large surges, health departments may focus on high-risk settings like nursing homes or schools. The passage concludes that contact tracing combines science, planning, and community support.
Which statement best describes how the central idea about trust is developed in the passage?
- It is developed by explaining why some people may hold back information and by giving examples of steps health departments take to increase cooperation. (correct answer)
- It is developed by claiming that trust matters most when case numbers rise, and by giving examples of how large surges force workers to skip building cooperation.
- It is developed by explaining that trust grows automatically over time, and by giving examples of diseases that spread quickly from one person to the next.
- It is developed by describing why people fear job loss, and by giving examples of the exact medical tests used to confirm whether a person is truly sick.
Explanation: An author develops a central idea through the reasons and examples given for it. Here, the trust idea grows from an explanation of why people might hold back information, such as fearing blame or job loss, followed by examples of steps that build cooperation, like protecting privacy and offering food or housing. The best answer names both of those moves. Another choice claims trust matters most during surges and that workers skip cooperation then, but the passage says surges only shift focus to high-risk settings, not that trust is abandoned. A different choice says trust grows automatically and lists diseases spreading quickly, but the passage never says trust is automatic and does not build the trust idea from disease spread. The last wrong choice mentions job-loss fears but then points to exact medical tests, which the passage never describes, so it does not develop the trust idea.
Question 19
When people talk about renewable energy, they often focus on the type of technology, such as solar panels, wind turbines, or dams. The bigger question, though, is what these sources replace. Electricity made by burning coal or natural gas releases carbon dioxide, a gas that traps heat in the air. Solar and wind make electricity without releasing that gas as they run. So switching to them can lower how much a place pollutes.
There is a second idea to think about. Renewable energy can be costly at first, but it may save money over time. Building wind farms or putting solar panels on a roof takes a lot of money up front. Yet once they are set up, the fuel is free, because wind and sunlight cost nothing. Repair costs can also stay steady. Over many years, the total cost can match the cost of fossil fuels, especially when fuel prices rise.
Renewables also need careful planning. Because wind and sunlight change, power companies may add batteries, link to larger grids, or keep a few flexible power plants ready. These steps help keep the electricity steady while pollution goes down.
How does the passage develop the idea that renewable energy can save money over time?
- By listing several different renewable technologies and explaining in careful detail exactly how each one works.
- By comparing the upfront costs with long-term factors like free fuel and steady maintenance, showing how the total cost can become competitive. (correct answer)
- By arguing that fossil fuels are going to run out very soon, which would make renewables the only choice left.
- By focusing mainly on how batteries store extra energy for later, while ignoring the question of cost entirely.
Explanation: To trace how an idea is developed, follow the reasoning the passage lays out. For the money idea, it first admits the high upfront cost, then explains the long-term savings, free fuel and steady repair costs, and concludes that the total cost can match fossil fuels over time. Choice B describes that development, so it is correct. Choice A describes a how-it-works structure the passage does not use, Choice C invents an argument about fossil fuels running out, and Choice D narrows the passage to batteries while dropping cost.
Question 20
Before a drought is obvious, it often begins quietly. The passage explains that drought is not only no rain. It is a long period when the water supply falls below what people and nature need. Scientists track rainfall, soil moisture, river levels, and mountain snowpack. Melting snow feeds many rivers in spring and summer.
A second central idea is that drought affects many parts of society. These parts are connected. Farmers may struggle to water crops. That can lower harvests and raise food prices. Cities may limit lawn watering or car washing to save water. Hydroelectric dams can make less electricity when reservoirs drop. That may force power companies to use other energy sources.
The passage also describes how communities respond. Some regions build water storage systems, repair leaking pipes, and plant drought-tolerant gardens. Others reuse treated wastewater for farms or industry. The passage concludes that understanding drought measurements helps leaders plan. Good plans reduce harm to both people and the environment.
Which option best summarizes the passage objectively?
- The passage describes how drought is measured with several indicators and explains how it affects farming, cities, and energy while prompting different responses. (correct answer)
- The passage focuses mainly on how melting snowpack feeds rivers, arguing that careful farming alone could prevent most droughts from ever harming communities.
- The passage explains how communities repair pipes and reuse wastewater, claiming these responses matter more than measuring rainfall, soil, or reservoir levels.
- The passage describes several ways to track drought and its effects, concluding that leaders can now predict exactly when and where the next drought will strike.
Explanation: An objective summary covers the whole passage's main points without twisting them or adding opinions. The correct choice fairly captures all three ideas: how drought is measured, how it affects farming, cities, and energy, and how communities respond. The choice about snowpack takes one small detail and overstates it, then adds the false claim that careful farming alone could prevent most droughts—the passage never blames farmers or promises prevention. The choice about repairing pipes and reusing wastewater covers only the response section and wrongly ranks those actions above measurement, a judgment the passage never makes. The choice about predicting droughts starts accurately but ends with a claim the passage never supports: it says measurements help leaders plan, not that anyone can predict exactly when and where the next drought will hit. Only the first choice summarizes the full passage without distortion.