Determine Main Ideas and Summarize
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5th Grade Reading › Determine Main Ideas and Summarize
Read the passage, then answer the question.
Coral reefs may look like colorful rocks, but they are living communities built by tiny animals called coral polyps. One main idea is that reefs support many ocean species. Polyps build hard skeletons that stack up over time, forming reefs with caves and cracks. Fish, crabs, and sea stars use these spaces to hide from predators and to find food. Although reefs cover less than 1% of the ocean floor, scientists estimate they support about a quarter of all marine species.
Another main idea is that coral reefs protect coastlines. When waves reach a reef, the rough surface breaks up the wave energy. This can reduce beach erosion and help protect buildings during storms. Some islands depend on reefs as a natural barrier because they have few other defenses against strong waves.
However, reefs face serious threats. Warmer ocean water can cause coral bleaching, when corals lose the algae that give them color and energy. Pollution and muddy runoff can block sunlight and make it harder for corals to grow. Overfishing can also harm reefs by removing fish that keep algae from taking over. People are working on solutions, such as creating marine protected areas and reducing pollution from land.
Which statement best describes the two main ideas of this passage?
Coral reefs are built by coral polyps, and coral bleaching happens when corals lose their algae.
Overfishing is the biggest threat to coral reefs in every ocean.
Reefs cover less than 1% of the ocean floor, and fish hide in reef cracks.
Coral reefs help many ocean species and protect coastlines, but they are threatened and need protection.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about identifying the main ideas. This passage contains 3 main ideas about coral reefs: (1) Reefs support many ocean species by providing habitat, (2) Coral reefs protect coastlines by breaking up wave energy, and (3) Reefs face serious threats like bleaching and pollution. However, the question asks specifically for two main ideas. Choice B is correct because it accurately identifies the two most prominent main ideas: coral reefs help many ocean species and protect coastlines, while also acknowledging they are threatened and need protection. These are the big ideas the passage is mostly about, combining the positive roles with the challenges. Choice A represents too specific a focus. Students who select this may have confused supporting details (how reefs are built, what bleaching is) with the main ideas about what reefs do and why they matter. To help students identify main ideas: (1) Teach distinction between TOPIC (what it's about, one word or phrase), MAIN IDEA (most important point about topic, complete sentence or phrase), and DETAILS (facts that support main idea). (2) Ask: What is this section mostly about? Not just topic, but what about the topic? (3) Check each paragraph's topic sentence (usually first or last sentence). (4) For multiple main ideas: Ask if ideas are about different aspects—if yes, likely separate main ideas; if saying same thing different ways, likely one main idea. (5) Use graphic organizer: Circle topic in center, draw 2-3 main branches for main ideas, smaller branches for key details. (6) Test if it's main idea: Remove it—would you still understand passage? If no, it's probably a main idea. Common difficulty: Students often confuse topic (coral reefs) with main idea (coral reefs support ocean life), or list details instead of stating big ideas.
Read the passage, then answer the question.
Plastic pollution is a growing environmental issue in oceans, rivers, and even on land. One main idea is that plastic enters the environment in many ways. Some trash blows out of bins or falls from trucks. Storm drains can carry litter into waterways after heavy rain. Fishing gear, such as nets and lines, may also be lost at sea. Because many plastics do not break down quickly, they can remain in the environment for decades.
Another main idea is that plastic harms wildlife and ecosystems. Animals may mistake plastic pieces for food and become sick or starve. Birds and sea turtles can get tangled in rings, ropes, or nets, making it hard to swim or fly. As plastic breaks into tiny pieces called microplastics, it can mix into sand and water. Scientists have found microplastics in the stomachs of fish, which can affect the food chain.
A third main idea is that people can reduce plastic pollution with solutions at home and in communities. Using reusable bottles and bags lowers the amount of plastic thrown away. Some cities improve recycling programs and add trash traps to storm drains. Companies are also testing new packaging made from materials that break down more easily. Cleanups along beaches and rivers help, but preventing plastic waste in the first place makes the biggest difference.
Which information is essential to understanding the main idea that plastic harms wildlife and ecosystems?
Animals can mistake plastic for food or get tangled in it, and microplastics can enter the food chain.
Companies are testing new packaging made from materials that break down more easily.
Cleanups along beaches and rivers can be fun community events.
Some trash blows out of bins or falls from trucks on windy days.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about key details supporting a specific main idea. This passage contains 3 main ideas about plastic pollution: (1) Plastic enters the environment in many ways, (2) Plastic harms wildlife and ecosystems, and (3) People can reduce plastic pollution with various solutions. The question asks specifically about details supporting the second main idea about harm to wildlife and ecosystems. Choice A is correct because this detail is essential to understanding how plastic harms wildlife and ecosystems. This fact provides critical evidence by explaining two key ways plastic causes harm: animals mistake it for food (causing sickness/starvation) and get tangled in it, plus microplastics enter the food chain. Choice B represents a detail supporting the wrong main idea. Students who select this may have chosen a detail but not recognized it supports how plastic enters the environment, not how it harms wildlife. To help students identify key details: (1) Teach hierarchy: MAIN IDEA (big idea), KEY DETAILS (essential facts that support it), SUPPORTING DETAILS (add info but not essential), MINOR DETAILS (interesting but not important). (2) Test importance: If I removed this detail, would I still understand the main idea? If no, it's probably a key detail. (3) Ask: Does this explain HOW? Does it explain WHY? Does it give critical example or evidence? If yes, likely key. (4) Practice sorting details into KEY (must include in summary) vs. SUPPORTING (could include) vs. MINOR (omit). (5) Look for details that directly answer questions about the main idea.
Read the passage, then answer the question.
In the 1800s, many people moved west across the United States. One main idea is that several factors encouraged this movement. Some families wanted farmland, and the government offered land through laws like the Homestead Act. Others hoped to find jobs in new towns or to join family members who had already moved. News stories about gold and other resources also attracted people, even though success was not guaranteed.
Another main idea is that traveling west was difficult and required planning. Many settlers used wagon trails, which could take months to cross. People needed food, tools, and spare parts for wagons. Rivers, mountains, and bad weather could slow travel or force groups to change routes. Illness was also a problem, so some travelers formed wagon trains to share supplies and help each other.
Finally, westward movement changed the country. New states entered the United States, and railroads connected distant regions. However, expansion also harmed many Native American nations. As more settlers arrived, Native people lost land and resources that they depended on. Today, historians study many viewpoints to understand how westward movement affected different groups.
Which statement best summarizes the passage?
Many settlers traveled in wagon trains because rivers and mountains made the journey difficult.
The Homestead Act offered land, and gold stories made success seem guaranteed for settlers.
Railroads were built to connect distant regions, and new states entered the United States.
People moved west for land and opportunity, faced major challenges during travel, and caused lasting changes that helped some groups but harmed Native American nations.
Explanation
This question assesses CCSS.RI.5.2: summarizing the text. This asks about creating a summary of the entire passage. This passage contains 3 main ideas about westward movement in the 1800s: (1) Several factors encouraged westward movement including land opportunities and gold, (2) Traveling west was difficult and required planning with challenges like terrain and illness, and (3) Westward movement changed the country but also harmed Native American nations. Each main idea is supported by key details. For example, the encouragement factors are supported by details about the Homestead Act and gold rush stories. Choice B is correct because it includes all 3 main ideas—people moved west for land and opportunity, faced major challenges during travel, and caused lasting changes that helped some groups but harmed Native American nations—with the most important supporting information, while omitting less essential details. This captures what the passage is mostly about in a brief statement. Choice A represents only one part of the passage. Students who select this may have summarized only the middle section about travel difficulties instead of including all three main ideas about reasons, challenges, and consequences of westward movement. To help students write summaries: (1) Teach summary rules: Include ALL main ideas, add most important key details, omit supporting/minor details, much shorter than original, in your own words. (2) Use 'Main Idea + Key Detail + Main Idea + Key Detail' formulas. (3) Model: Read passage, identify 2-3 main ideas, select 1-2 most important details per main idea, write 3-5 sentences combining them. (4) Practice deleting: Start with retelling, then delete least important sentence each time until only essentials remain. (5) Check summary: Does it include all main ideas? Does it omit minor details? Could someone understand the passage from just this? Common difficulties: Students often (a) retell everything (include too many details), (b) omit one main idea (incomplete), or (c) stay too vague (only state topic). Teach specific but brief.
Read the passage, then answer the question.
When people talk about the water cycle, they are describing how water moves on, above, and below Earth’s surface. One main idea is that the cycle is powered by the sun. Sunlight warms oceans, lakes, and even wet soil. This causes evaporation, when liquid water changes into water vapor. Plants also release water vapor through transpiration. Together, these processes add moisture to the air.
Another main idea is that water changes form and returns to Earth. As warm, moist air rises, it cools. The water vapor condenses into tiny droplets, forming clouds. When droplets grow heavy, precipitation falls as rain, snow, sleet, or hail. Some precipitation runs over land into rivers, and some soaks into the ground to become groundwater.
Finally, the water cycle matters because it affects weather and supplies fresh water. Storms form when warm, wet air meets cooler air. Snowpack in mountains can act like a natural storage system that melts in spring. People build reservoirs to store water, but they still depend on the cycle to refill them. Even though the same water keeps moving around, clean freshwater is limited in many places.
What are the three main ideas in this passage?
The water cycle is important because storms are dangerous and hail can damage cars.
Clouds form when air rises, and precipitation falls as rain, snow, sleet, or hail.
The sun powers evaporation and transpiration; water condenses and falls as precipitation; and the water cycle affects weather and freshwater supplies.
Reservoirs store water, and snowpack melts in spring in many mountain areas.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about identifying all main ideas. This passage contains 3 main ideas about the water cycle: (1) The cycle is powered by the sun through evaporation and transpiration, (2) Water changes form and returns to Earth as precipitation, and (3) The water cycle matters because it affects weather and supplies fresh water. Each main idea is supported by key details. For example, the sun-powered idea is supported by details about how sunlight warms water causing evaporation. Choice A is correct because it accurately identifies all 3 main ideas: the sun powers evaporation and transpiration, water condenses and falls as precipitation, and the water cycle affects weather and freshwater supplies. These are the big ideas the passage is mostly about, not just minor details or the topic alone. Choice B represents details not main ideas. Students who select this may have focused on specific processes (cloud formation, types of precipitation) instead of identifying the overall main ideas about how the cycle works and why it matters. To help students identify main ideas: (1) Teach distinction between TOPIC (what it's about, one word or phrase), MAIN IDEA (most important point about topic, complete sentence or phrase), and DETAILS (facts that support main idea). (2) Ask: What is this section mostly about? Not just topic, but what about the topic? (3) Check each paragraph's topic sentence (usually first or last sentence). (4) For multiple main ideas: Ask if ideas are about different aspects—if yes, likely separate main ideas; if saying same thing different ways, likely one main idea. (5) Use graphic organizer: Circle topic in center, draw 2-3 main branches for main ideas, smaller branches for key details. (6) Test if it's main idea: Remove it—would you still understand passage? If no, it's probably a main idea. Common difficulty: Students often confuse topic (water cycle) with main idea (the cycle is powered by the sun), or list details instead of stating big ideas.
Read the passage, then answer the question.
A solar oven is a device that cooks food using energy from the sun. One main idea is that solar ovens work by collecting and trapping heat. Many designs use shiny panels to reflect sunlight toward a dark pot. Dark surfaces absorb more light and turn it into heat. A clear lid or plastic cover helps trap warm air inside, like a greenhouse. On a sunny day, some solar ovens can reach temperatures hot enough to cook rice, vegetables, or even bake simple bread.
Another main idea is that solar ovens can help families save fuel and reduce pollution. In places where people cook with wood or charcoal, finding fuel can take time and money. Burning wood also creates smoke that can harm lungs, especially in small kitchens. Using sunlight for cooking can lower the amount of fuel needed, which may reduce deforestation in some regions. However, solar ovens do not work well at night or during heavy clouds, so many families use them along with other stoves.
Finally, building a solar oven can teach engineering and problem-solving. Students test different angles for the reflectors, measure cooking time, and compare temperatures. Small changes—like sealing gaps where air leaks—can make a big difference. In a class project, Jamal noticed his oven heated faster after he added extra insulation under the cooking chamber.
Which detail best supports the main idea that solar ovens work by collecting and trapping heat?
Jamal added extra insulation under the cooking chamber during a class project.
Burning wood creates smoke that can harm lungs, especially in small kitchens.
Many designs use shiny panels to reflect sunlight toward a dark pot, and a clear cover traps warm air inside.
Solar ovens do not work well at night or during heavy clouds.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about key details supporting a specific main idea. This passage contains 3 main ideas about solar ovens: (1) Solar ovens work by collecting and trapping heat, (2) Solar ovens can help families save fuel and reduce pollution, and (3) Building a solar oven can teach engineering and problem-solving. The question asks specifically about details supporting the first main idea about how solar ovens work. Choice A is correct because this detail is essential to supporting the main idea that solar ovens work by collecting and trapping heat. This fact provides critical evidence by explaining the two key mechanisms: shiny panels reflect sunlight (collecting) and a clear cover traps warm air inside (trapping). Choice B represents a detail supporting the wrong main idea. Students who select this may have chosen an important detail but not recognized it supports the fuel-saving main idea, not the how-they-work main idea. To help students identify key details: (1) Teach hierarchy: MAIN IDEA (big idea), KEY DETAILS (essential facts that support it), SUPPORTING DETAILS (add info but not essential), MINOR DETAILS (interesting but not important). (2) Test importance: If I removed this detail, would I still understand the main idea? If no, it's probably a key detail. (3) Ask: Does this explain HOW? Does it explain WHY? Does it give critical example or evidence? If yes, likely key. (4) Practice sorting details into KEY (must include in summary) vs. SUPPORTING (could include) vs. MINOR (omit). (5) Look for details that directly answer questions about the main idea.
Read the passage, then answer the question.
In many cities, people are adding green roofs (roofs covered with plants) to buildings. One main idea is that green roofs help manage rainwater. When rain falls on a regular roof, water runs quickly into storm drains and can cause flooding. On a green roof, soil and plants absorb water like a sponge. Some green roofs can hold back more than half of the rain from a small storm. The extra water slowly drains out later, which helps keep sewers from overflowing. As a bonus, the plants can filter some dirt and chemicals from the water before it reaches rivers.
Another main idea is that green roofs make buildings more energy-efficient. In summer, dark roofs soak up heat from the sun. A green roof shades the roof surface and cools the air through evaporation. This can lower indoor temperatures and reduce the need for air conditioning. In winter, the soil layer adds insulation, helping buildings keep warm air inside. A school in one city reported lower energy bills after adding a green roof, although results can vary by building size and local weather.
A third main idea is that green roofs support living things in crowded places. Cities often have fewer natural habitats because of pavement and tall buildings. Green roofs can provide food and shelter for insects and birds. Some roofs are planted with native flowers to attract pollinators like bees. However, not every roof can hold heavy soil, so engineers must check safety first. People also need to plan for maintenance, such as weeding and watering during dry weeks.
Which statement best summarizes the entire passage?
Green roofs look nice, but they need watering and weeding during dry weeks.
Green roofs help cities by absorbing rainwater, saving building energy, and providing habitat, but they must be safely designed and maintained.
Engineers should check every roof because soil can be heavy and may damage buildings.
Dark roofs soak up heat, and green roofs cool the air through evaporation in summer.
Explanation
This question assesses CCSS.RI.5.2: summarizing the text. This asks about creating a summary of the entire passage. This passage contains 3 main ideas about green roofs: (1) Green roofs help manage rainwater by absorbing it like a sponge, (2) Green roofs make buildings more energy-efficient by cooling in summer and insulating in winter, and (3) Green roofs support living things by providing habitat in crowded cities. Each main idea is supported by key details. For example, the rainwater management idea is supported by the detail that green roofs can hold back more than half the rain from small storms. Choice B is correct because it includes all 3 main ideas—absorbing rainwater, saving building energy, and providing habitat—with the most important supporting information about safety and maintenance, while omitting less essential details. This captures what the passage is mostly about in a brief statement. Choice A represents an incomplete summary. Students who select this may have focused on only one aspect (appearance and maintenance) instead of including all three main ideas about the benefits of green roofs. To help students write summaries: (1) Teach summary rules: Include ALL main ideas, add most important key details, omit supporting/minor details, much shorter than original, in your own words. (2) Use 'Main Idea + Key Detail + Main Idea + Key Detail' formulas. (3) Model: Read passage, identify 2-3 main ideas, select 1-2 most important details per main idea, write 3-5 sentences combining them. (4) Practice deleting: Start with retelling, then delete least important sentence each time until only essentials remain. (5) Check summary: Does it include all main ideas? Does it omit minor details? Could someone understand the passage from just this? Common difficulties: Students often (a) retell everything (include too many details), (b) omit one main idea (incomplete), or (c) stay too vague (only state topic). Teach specific but brief.
Read the passage, then answer the question.
The International Space Station (ISS) is a large science lab that orbits Earth about 250 miles above the ground. One main idea is that the ISS is built through teamwork. The station includes parts made by the United States, Russia, Japan, Canada, and several European countries. Astronauts from different nations train together and share jobs, such as repairing equipment and running experiments. Supplies arrive on cargo spacecraft, and crews rotate every few months.
Another main idea is that the ISS allows scientists to study how things behave in microgravity (very low gravity). Without normal gravity, liquids form floating spheres, flames burn differently, and muscles weaken if astronauts do not exercise. Researchers test new materials, study plant growth, and learn how the human body changes in space. These studies help scientists plan for longer missions, like traveling to Mars.
Finally, the ISS benefits life on Earth. Some research has improved water filters and ways to monitor air quality. The station also takes photos of Earth that help scientists track storms, wildfires, and changes in ice. Many students talk with astronauts during live events, which can inspire them to study science and engineering.
Which detail is most important for supporting the main idea that the ISS helps scientists learn in microgravity?
Researchers study plant growth and how the human body changes when gravity is very low.
Students can talk with astronauts during live events from the station.
Astronauts from different nations train together and share jobs on the station.
The ISS orbits Earth about 250 miles above the ground.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about key details supporting a specific main idea. This passage contains 3 main ideas about the International Space Station: (1) The ISS is built through international teamwork, (2) The ISS allows scientists to study how things behave in microgravity, and (3) The ISS benefits life on Earth through research and education. The question asks specifically about details supporting the second main idea about microgravity research. Choice B is correct because this detail is essential to supporting the main idea that the ISS helps scientists learn in microgravity. This fact provides critical evidence by giving specific examples of what scientists study (plant growth and human body changes) and explains why microgravity research is important. Choice A represents a detail supporting the wrong main idea. Students who select this may have chosen an interesting detail but not recognized it supports the teamwork main idea, not the microgravity research main idea. To help students identify key details: (1) Teach hierarchy: MAIN IDEA (big idea), KEY DETAILS (essential facts that support it), SUPPORTING DETAILS (add info but not essential), MINOR DETAILS (interesting but not important). (2) Test importance: If I removed this detail, would I still understand the main idea? If no, it's probably a key detail. (3) Ask: Does this explain HOW? Does it explain WHY? Does it give critical example or evidence? If yes, likely key. (4) Practice sorting details into KEY (must include in summary) vs. SUPPORTING (could include) vs. MINOR (omit). (5) Look for details that directly answer questions about the main idea.
Read the passage, then answer the question.
A community garden is a shared space where neighbors grow fruits, vegetables, and flowers together. One main idea is that community gardens can improve access to fresh food. In some neighborhoods, grocery stores with produce are far away. Garden plots allow families to grow tomatoes, beans, and greens close to home. Many gardens donate extra harvest to food pantries or share it at neighborhood events. Fresh food can also help people try new recipes and eat more vegetables.
Another main idea is that community gardens build stronger communities. Gardeners often work side by side, which gives them chances to meet new neighbors. People share tools, trade seeds, and teach each other planting skills. Some gardens create teams for watering schedules, so plants do not dry out during hot weeks. Schools sometimes visit gardens for science lessons, and older gardeners may share stories about how farming worked when they were young.
Finally, community gardens can help the environment in small but real ways. Plants absorb carbon dioxide and release oxygen. Garden soil can soak up rainwater, which reduces runoff on sidewalks and streets. When gardeners compost food scraps, they keep waste out of landfills and create rich soil. However, gardens still need planning, like testing soil for safety and setting rules so everyone uses the space fairly.
Which two ideas are most important to understanding this passage?
Older gardeners may share stories, and schools sometimes visit gardens for science lessons.
Community gardens grow tomatoes, beans, and greens, and gardeners must make watering schedules.
Community gardens can provide fresh food and bring neighbors together, and they can also offer environmental benefits when they are well planned.
Composting creates rich soil, and gardens should set rules so everyone uses the space fairly.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about identifying the two most important main ideas. This passage contains 3 main ideas about community gardens: (1) Community gardens can improve access to fresh food, (2) Community gardens build stronger communities through shared work and interaction, and (3) Community gardens can help the environment in small but real ways. The question asks for the two most important ideas. Choice A is correct because it accurately identifies the two primary main ideas: community gardens provide fresh food and bring neighbors together, plus it acknowledges the environmental benefits when well planned. These capture the essential purposes and benefits of community gardens. Choice B represents details not main ideas. Students who select this may have focused on specific examples (types of vegetables grown, watering schedules) instead of identifying the overall main ideas about how gardens improve food access and build community. To help students identify main ideas: (1) Teach distinction between TOPIC (what it's about, one word or phrase), MAIN IDEA (most important point about topic, complete sentence or phrase), and DETAILS (facts that support main idea). (2) Ask: What is this section mostly about? Not just topic, but what about the topic? (3) Check each paragraph's topic sentence (usually first or last sentence). (4) For multiple main ideas: Ask if ideas are about different aspects—if yes, likely separate main ideas; if saying same thing different ways, likely one main idea. (5) Use graphic organizer: Circle topic in center, draw 2-3 main branches for main ideas, smaller branches for key details. (6) Test if it's main idea: Remove it—would you still understand passage? If no, it's probably a main idea. Common difficulty: Students often confuse topic (community gardens) with main idea (gardens improve food access), or list details instead of stating big ideas.
Read the passage, then answer the question.
A watershed is an area of land where all the water drains to the same place, such as a river, lake, or ocean. One main idea is that watersheds connect places that may seem far apart. Rain that falls on a hill can flow into a small stream, then into a larger river, and finally into a bay. Because of this, actions upstream can affect people and animals downstream. For example, if trash is left near a creek, it can travel and pile up along riverbanks many miles away.
Another main idea is that watersheds are shaped by land features. Ridges and mountains often form boundaries between watersheds, like lines that separate different bowls. Water flows downhill because of gravity, so the steepness of the land changes how fast water moves. In flat areas, water may spread into wetlands that act like natural sponges. Wetlands can slow floods and provide homes for frogs, fish, and birds.
A third main idea is that people can protect watersheds with simple choices. Planting trees and grasses helps hold soil in place, which reduces erosion. Building rain gardens allows water to soak into the ground instead of rushing into storm drains. Communities also test water for pollution and set rules for factories and farms. Even small actions, like picking up litter or using less fertilizer, can keep waterways cleaner.
Which statement best expresses the main ideas of the text?
Trash left near a creek can travel many miles and pile up along riverbanks.
Watersheds are areas where water drains to the same place, they are shaped by land features, and people can take steps to protect them.
Gravity pulls water downhill, so water always moves quickly through steep areas.
Wetlands are natural sponges that slow floods and provide homes for many animals.
Explanation
This question assesses CCSS.RI.5.2: determining two or more main ideas of a text and explaining how they are supported by key details. This asks about identifying the main ideas. This passage contains 3 main ideas about watersheds: (1) Watersheds connect places that may seem far apart, (2) Watersheds are shaped by land features like ridges and steepness, and (3) People can protect watersheds with simple choices like planting trees and building rain gardens. Each main idea is supported by key details. For example, the connection idea is supported by the detail that trash left near a creek can travel many miles downstream. Choice A is correct because it accurately identifies the 3 main ideas: watersheds are areas where water drains to the same place, they are shaped by land features, and people can take steps to protect them. These are the big ideas the passage is mostly about, not just minor details or the topic alone. Choice B represents a detail not an idea. Students who select this may have focused on one interesting detail about wetlands instead of identifying the overall main ideas about watersheds. To help students identify main ideas: (1) Teach distinction between TOPIC (what it's about, one word or phrase), MAIN IDEA (most important point about topic, complete sentence or phrase), and DETAILS (facts that support main idea). (2) Ask: What is this section mostly about? Not just topic, but what about the topic? (3) Check each paragraph's topic sentence (usually first or last sentence). (4) For multiple main ideas: Ask if ideas are about different aspects—if yes, likely separate main ideas; if saying same thing different ways, likely one main idea. (5) Use graphic organizer: Circle topic in center, draw 2-3 main branches for main ideas, smaller branches for key details. (6) Test if it's main idea: Remove it—would you still understand passage? If no, it's probably a main idea. Common difficulty: Students often confuse topic (watersheds) with main idea (watersheds connect distant places), or list details instead of stating big ideas.
Read the passage.
A volcano is an opening in Earth’s crust where melted rock, gas, and ash can escape. The melted rock underground is called magma. When magma reaches the surface, it is called lava. Volcanoes often form near the edges of tectonic plates, where plates push together or pull apart.
Another main idea is how volcanoes erupt. Gas builds up pressure inside magma, like bubbles in a shaken soda. If pressure becomes too strong, magma can break through rock and shoot upward. Some eruptions are slow, with lava flowing like thick syrup. Others are explosive and send ash high into the sky.
Volcanoes can also change the land and affect people. Lava can create new land as it cools into rock. Volcanic ash can make soil rich, which helps farmers grow crops later. However, ash can also make air hard to breathe and can damage engines. Communities near volcanoes use monitoring tools, such as seismographs, to detect small earthquakes that may happen before an eruption.
Finally, scientists study volcanoes to improve safety. They measure gas, ground movement, and heat to understand what is happening underground. Warning systems can help people evacuate in time. Even though volcanoes can be dangerous, learning about them helps communities prepare.
Which detail is most important for supporting the main idea that volcanoes erupt because pressure builds up underground?
Volcanoes often form near the edges of tectonic plates.
Volcanic ash can make soil rich, which helps farmers grow crops later.
Gas builds up pressure inside magma, like bubbles in a shaken soda.
Some eruptions are slow, with lava flowing like thick syrup.
Explanation
This question assesses CCSS.RI.5.2: determining how key details support main ideas. This asks about key details. The passage's second main idea explains how volcanoes erupt, specifically that gas builds up pressure inside magma until it breaks through. Key details that support this main idea include the comparison to bubbles in shaken soda and the explanation that pressure can become too strong and break through rock. Choice B is correct because this detail is essential to supporting the main idea that volcanoes erupt because pressure builds up underground. This fact provides critical evidence by giving a concrete comparison that helps readers understand how gas pressure works inside magma—just like shaking a soda creates pressure from bubbles that can cause an explosive release. Choice D represents a wrong main idea error. Students who select this may have chosen a detail that supports a different main idea (about where volcanoes form) rather than the specific main idea about how pressure causes eruptions. To help students identify key details: (1) Teach hierarchy: MAIN IDEA (big idea), KEY DETAILS (essential facts that support it), SUPPORTING DETAILS (add info but not essential), MINOR DETAILS (interesting but not important). (2) Test importance: If I removed this detail, would I still understand the main idea? If no, it's probably a key detail. (3) Ask: Does this explain HOW? Does it explain WHY? Does it give critical example or evidence? If yes, likely key. (4) Practice sorting details into KEY (must include in summary) vs. SUPPORTING (could include) vs. MINOR (omit). (5) Look for details that directly answer questions about the main idea.