- The passage mentions that during the Civil War, Harriet Tubman served the Union Army in all of the following roles EXCEPT:
Answer: General
This is an "EXCEPT" question, which means you need to identify what is NOT mentioned in the passage. These questions require careful attention to what's explicitly stated versus what might seem logical but isn't actually there.
Looking at the passage, it clearly states that during the Civil War, Harriet Tubman "served the Union Army as a cook, a nurse, and eventually as an armed scout and spy." This gives you three specific roles that are directly mentioned in the text.
Now examining each answer choice: Choice A (Nurse) is explicitly mentioned in the passage as one of her roles. Choice C (Spy) is also directly stated - the passage says she served "as an armed scout and spy." Choice D (Cook) appears first in the list of her Union Army roles. However, choice B (General) is nowhere to be found in the passage. While Tubman was certainly a leader and strategist, the passage never mentions her holding the military rank of general.
The trap in "EXCEPT" questions is often that wrong answers include roles or facts that seem plausible based on what you know about the person, even if they're not in the passage. Tubman was indeed a remarkable leader, so "general" might sound reasonable, but you must stick strictly to what the text actually says.
For EXCEPT questions on the HSPT, always go back to the passage and check off each choice that IS mentioned. The one you can't find is your answer. Don't rely on outside knowledge - only use what's explicitly stated in the text.
- What is the stated function of a tuned mass damper (TMD) in a skyscraper?
Answer: To stabilize the tower by swinging in opposition to its wind-induced sway.
When you encounter reading comprehension questions about technical passages, focus on finding information that is explicitly stated rather than making inferences. This question asks for the "stated function" of a tuned mass damper, so you need to locate where the passage directly explains what a TMD does.
The passage clearly describes the TMD's purpose: "The TMD is designed to swing in opposition to the building's sway, absorbing the vibrational energy from the wind and dissipating it, thus keeping the tower stable." This directly supports answer choice C, which correctly identifies that the TMD stabilizes the tower by swinging opposite to wind-induced sway.
Looking at the wrong answers: Choice A incorrectly suggests the TMD generates electricity. While the passage mentions the TMD absorbs and dissipates wind energy, it never states this energy is converted to electricity. Choice B claims the TMD provides structural support for the steel frame, but the passage explains that the steel frame carries the building's weight independently—the TMD specifically addresses the separate problem of wind sway. Choice D mentions seismic disturbances, but the passage only discusses wind-related motion, not earthquakes.
The key trap here is confusing related but distinct concepts. The TMD deals with wind sway, not structural support or electricity generation. When tackling technical reading passages, always distinguish between the specific problem being solved and the general context. Look for precise language matches between the question and passage rather than assuming broader applications of the technology described.
- The passage lists which of the following as an application of sonar technology?
Answer: Detecting enemy submarines
This question tests your ability to identify specific information directly stated in a passage. When facing reading comprehension questions that ask what a passage "lists" or "mentions," you need to locate explicit details rather than make inferences.
Looking at the final sentence of the passage, you can see that sonar technology is described as "vital for mapping the ocean floor, locating underwater hazards, and military operations such as detecting enemy submarines." The phrase "detecting enemy submarines" appears word-for-word, making choice B correct.
Now let's examine why the other options are wrong. Choice A (predicting underwater earthquakes) is never mentioned in the passage as a sonar application. The passage focuses on navigation, detection, and mapping functions, not seismic prediction. Choice C (studying the chemical composition of seawater) also doesn't appear anywhere in the text. While sonar deals with underwater environments, the passage specifically describes it as using sound waves for detection and ranging, not chemical analysis. Choice D (tracking the migration of birds) is particularly off-target since the entire passage focuses on underwater and marine applications—sonar technology operates in water, not air.
For HSPT reading questions that ask what a passage "lists" or "states," always look for exact matches or very close paraphrases of the text. Don't overthink these questions by trying to infer connections that aren't explicitly made. Stick to what's directly written, and you'll avoid the trap answers that sound plausible but aren't actually supported by the passage.
- The passage states that the American engineering plan differed from the French plan in that the Americans decided to...
Answer: use a series of locks and an artificial lake to manage the land's different elevations.
This question tests your ability to identify specific details and contrasts presented in a reading passage. When you encounter comparison questions, look for signal words like "instead," "abandoned," or "differed from" that highlight key distinctions.
The passage clearly states that "the American team abandoned the French plan for a sea-level canal. Instead, chief engineer John Stevens devised a system of massive locks to raise and lower ships across the varied elevations of the isthmus, creating the vast, artificial Gatun Lake in the process." This directly points to the core engineering difference: the Americans used locks and created an artificial lake to handle elevation changes, while the French had planned a sea-level canal.
Choice A is incorrect because it describes the French approach, not the American one. The French wanted a sea-level canal, but the Americans specifically abandoned this plan. Choice C mentions equipment differences, but the passage doesn't discuss steam shovels or dredging equipment as distinguishing factors between the two projects. Choice D refers to railroad construction, which isn't mentioned anywhere in the passage as part of either engineering plan.
The correct answer is B because it accurately captures the American innovation: using locks and an artificial lake (Gatun Lake) to manage the challenging terrain, rather than trying to dig straight through at sea level.
When tackling reading comprehension questions about contrasts or comparisons, always look for explicit transition words and phrases that signal differences. The word "instead" in this passage is your key clue pointing directly to how the American approach differed from the French plan.
- The passage explains that the velocipede was called the 'boneshaker' because of its...
Answer: rigid frame and iron-banded wheels.
When you encounter reading comprehension questions that ask about specific details, your job is to locate the exact information in the passage and match it precisely to the answer choices.
The passage directly states that the velocipede was called the 'boneshaker' because it was "so named for its rigid frame and iron-banded wheels that resulted in an uncomfortable ride." This explicit cause-and-effect relationship makes choice B correct—the rigid frame and iron-banded wheels were exactly what earned the velocipede its nickname.
Looking at the wrong answers: Choice A suggests the velocipede fell apart on rough roads, but the passage never mentions structural failure—only discomfort. Choice C mentions a heavy wooden frame, but the passage specifically describes a "rigid frame" without specifying the material, and the discomfort came from the frame's rigidity combined with iron-banded wheels, not from difficulty pedaling due to weight. Choice D attributes the nickname to high speed and dangerous design, but these characteristics actually describe the later "high-wheeler" or "penny-farthing" from the 1870s, not the 1860s velocipede.
For detail questions like this, always look for direct textual evidence rather than making inferences. The HSPT reading section often includes answer choices that mix up details from different parts of the passage or introduce plausible-sounding information that isn't actually stated. Train yourself to find the specific sentence that answers the question, then match it word-for-word with the answer choices.
- The sugar that a plant produces to serve as its food is called what?
Answer: Glucose
This question tests your ability to identify specific details from a science passage about photosynthesis. When you encounter reading questions about biological processes, focus on the technical terms and their definitions provided in the text.
The passage clearly states that "hydrogen is combined with carbon dioxide to produce glucose, a type of sugar" and then explains that "this glucose serves as the plant's food, providing energy for growth." The text directly identifies glucose as both the sugar produced and the food source for the plant.
Looking at the wrong answers: (A) Sucrose is indeed a type of sugar, but it's not mentioned anywhere in the passage as the product of photosynthesis. This choice might tempt you if you're drawing on outside knowledge of common sugars, but you must stick to what the passage tells you. (B) Chlorophyll is specifically identified in the text as "a green pigment" that "absorbs light energy" — it's part of the process, not the end product. (D) Fructose, like sucrose, is a real type of sugar but doesn't appear in this passage at all.
The correct answer is (C) glucose because it's the only option explicitly named in the passage as both the sugar produced during photosynthesis and the plant's food source.
For HSPT reading questions, always base your answers strictly on the information provided in the passage, even if you have outside knowledge about the topic. Look for direct statements that answer the question rather than making inferences when a literal answer is available.
- The passage states that cacao beans were used by Mayan and Aztec civilizations for what purpose besides consumption?
Answer: As a form of currency for trade and commercial transactions.
When you encounter reading comprehension questions that ask about specific details, you need to locate the exact information in the passage rather than making assumptions based on general knowledge.
The passage explicitly states that Mayan and Aztec civilizations "incorporated the beans into important ceremonies and even using them as a form of currency." This directly supports answer choice D - cacao beans served as currency for trade and commercial transactions alongside their ceremonial and consumption uses.
Let's examine why the other options are incorrect. Choice A suggests cacao beans were used as pigment for dyes, but the passage makes no mention of any coloring or textile applications. Choice B claims they were used as building material mixed with clay, which is never discussed in the text. Choice C proposes medicinal uses for skin treatments, but while the passage mentions the beans were consumed as a spiced beverage, it doesn't reference any medical applications.
These incorrect answers represent common traps on reading comprehension questions - they sound plausible based on what you might know about ancient civilizations or the properties of cacao, but they're not supported by the passage itself.
Remember this key strategy for detail questions: stick strictly to what's written in the passage. Don't let outside knowledge influence your answer choice. The correct information will be stated clearly in the text, just as "using them as a form of currency" appears directly after the question asks about purposes "besides consumption."
- What key innovation mentioned in the passage led to the development of the 'safety bicycle'?
Answer: A chain-driven rear wheel and equally sized wheels
When you encounter reading comprehension questions that ask about specific innovations or developments, you need to locate the exact information in the passage and match it precisely to the answer choices.
The passage clearly states that the invention of "the chain-driven rear wheel and equally sized wheels in the 1880s led to the 'safety bicycle.'" This direct statement makes choice A correct. The text explicitly connects these two innovations—the chain-driven rear wheel mechanism and wheels of equal size—to the development of the safety bicycle, which became "the direct ancestor of the bicycles we use today."
Let's examine why the other choices are incorrect. Choice B mentions rubber tires for comfort, but the passage never discusses rubber tires as an innovation. Choice C refers to lightweight aluminum frames, which also aren't mentioned anywhere in the text. Choice D identifies the addition of pedals to the front wheel, but the passage explains this innovation created the velocipede in the 1860s, not the safety bicycle of the 1880s.
The key trap here is choice D, which does represent a genuine innovation mentioned in the passage but connects it to the wrong bicycle type. This tests whether you're reading carefully enough to match specific innovations with their corresponding developments.
For HSPT reading questions about cause and effect or innovations, always look for explicit connecting language like "led to," "resulted in," or "created." The passage will typically state these relationships directly rather than requiring you to infer them.
- What was the estimated spectator capacity of the Colosseum?
Answer: 50,000 to 80,000
When you encounter reading comprehension questions asking for specific details, your task is to locate the exact information in the passage rather than making inferences or relying on outside knowledge.
The passage directly states that "The massive stone structure could hold an estimated 50,000 to 80,000 spectators." This explicit information makes choice A the correct answer. Notice how the question uses the exact phrase "estimated spectator capacity" that mirrors the passage's wording about what the structure "could hold."
Looking at the incorrect options: Choice B (25,000 to 40,000) provides numbers that are roughly half the actual capacity mentioned in the text. Choice C (10,000 to 20,000) dramatically underestimates the Colosseum's size, representing only about a quarter of the actual capacity. Choice D (Over 100,000) exceeds even the highest estimate given in the passage, since 80,000 is the upper limit mentioned.
These wrong answers likely test whether you're carefully reading the specific numbers or if you're guessing based on general impressions of the Colosseum's size. Notice that all the distractors use plausible ranges that might seem reasonable for a large ancient structure, but only one matches the passage.
Study tip: For detail-oriented questions like this, scan the passage for key words from the question stem. Here, "spectator capacity" should lead you directly to the sentence about what the structure "could hold." Don't second-guess explicit numerical information—if the passage gives specific figures, that's your answer.
- The spectators who stood in the central yard of the Globe were known by what name?
Answer: The groundlings
This question tests your ability to locate specific details directly stated in a reading passage. When you encounter questions asking for particular names, terms, or facts, your task is to scan the text for the exact information rather than make inferences.
The passage explicitly states that "the central yard, where the 'groundlings' stood, was open to the sky." This directly answers the question - the spectators who stood in the central yard were called "groundlings." The term appears in quotation marks, indicating it's a specific historical term that Shakespeare's theater used to describe these audience members.
Looking at the wrong answers: (B) "The yard-standers" is a logical-sounding term that describes what these people did, but it's not the actual historical name used. (C) "The commoners" might seem reasonable since standing tickets were cheaper than gallery seats, but this term doesn't appear in the passage and isn't the specific name being asked for. (D) "The penny-watchers" also sounds plausible as a period term for lower-paying customers, but again, this isn't mentioned anywhere in the text.
For HSPT reading questions asking for specific details, always look for exact matches between the question and passage text. Don't overthink or try to infer - if the question asks for a particular name or term, it will be stated directly in the passage. Scan efficiently by identifying key words from the question (here: "spectators," "central yard") and locating that section in the text.
- According to the passage, the Central Pacific Railroad largely depended on which group of laborers to build its portion of the line?
Answer: Chinese immigrants tasked with crossing the Sierra Nevada mountains.
This question tests your ability to locate specific factual information directly stated in a reading passage. When you encounter questions that ask "according to the passage," you should scan for explicit details rather than making inferences.
The passage clearly states that "the Central Pacific employed thousands of Chinese immigrants to tackle the treacherous terrain of the Sierra Nevada mountains." This directly identifies Chinese immigrants as the primary labor force for the Central Pacific Railroad's construction through the challenging mountain terrain.
Looking at the wrong answers: Choice A incorrectly attributes Civil War veterans to the Central Pacific, when the passage specifically states that the Union Pacific (not Central Pacific) relied on Civil War veterans. Choice B makes the same error with Irish immigrants—the passage indicates Irish immigrants worked for the Union Pacific, building westward from Omaha. Choice C suggests local western settlers, but this group isn't mentioned anywhere in the passage as part of either railroad's workforce.
The key distinction here is that the Union Pacific (building westward from Nebraska) used Irish immigrants and Civil War veterans, while the Central Pacific (building eastward from California) employed Chinese immigrants to navigate the difficult Sierra Nevada mountains.
When tackling reading comprehension questions on the HSPT, always return to the text to verify your answer. Don't rely on outside knowledge about historical events—stick strictly to what the passage tells you. Circle or underline key details as you read to make these fact-finding questions easier to answer quickly and accurately.
- What does the acronym SONAR stand for?
Answer: SOund NAvigation and Ranging
When you encounter questions asking for the meaning of acronyms, look directly at the passage first—the answer is often explicitly provided rather than requiring you to recall prior knowledge.
The passage clearly states in the opening sentence that "Sonar, an acronym for SOund NAvigation and Ranging, is a technique that uses sound propagation..." This directly gives you the full expansion of SONAR, making choice D correct.
Let's examine why the other options are wrong. Choice A (SOlar NAvigation and Radiation) incorrectly suggests sonar involves solar energy and radiation rather than sound waves. The passage emphasizes throughout that sonar uses "sound propagation" and "sound pulses," not solar technology. Choice B (SOlubale NAvigational Radar) contains the nonsensical word "solubale" and incorrectly identifies the technology as radar rather than sound-based ranging. Choice C (SOund NAnotechnology And Radar) correctly identifies that sonar uses sound but wrongly incorporates nanotechnology and radar, neither of which are mentioned in the passage.
For reading comprehension questions about definitions or acronyms, always scan the passage for explicit statements before trying to reason from context. Test makers often include the exact information you need in the text, especially for technical terms. When you see an acronym followed by "an acronym for" or similar phrasing, that's your cue that the definition is being provided directly.
- At which specific location did the two halves of the railroad finally connect?
Answer: Promontory Summit, Utah, the designated meeting point.
When you encounter reading comprehension questions asking for specific factual details, your goal is to locate the exact information in the passage rather than making inferences or relying on outside knowledge.
The passage explicitly states that "the two lines officially met at Promontory Summit, Utah, on May 10, 1869." This directly answers where the railroad connection occurred, making C the correct answer.
Let's examine why the other options are incorrect. Choice A mentions Sacramento, California, but the passage identifies this as the starting point for the Central Pacific Railroad building eastward, not the meeting location. Choice B references Omaha, Nebraska, which was the western starting point for the Union Pacific Railroad, again a beginning location rather than where the lines joined. Choice D suggests Salt Lake City, Utah, but while this city is in the same state as the actual meeting point, the passage makes no mention of Salt Lake City at all.
Notice how choices A and B are particularly tempting because they represent the two starting points of the railroad construction. This is a common pattern in reading comprehension questions—incorrect answers often include details that appear elsewhere in the passage but don't answer the specific question asked.
For HSPT reading questions, always scan for keywords from the question stem. Here, looking for words like "met," "connect," or "joining" would quickly lead you to the sentence containing "Promontory Summit, Utah." Don't overthink these factual questions—the answer is usually stated directly in the text.
- Which of the following events is mentioned in the passage as a type of public spectacle held at the Colosseum?
Answer: Mock sea battles
This question tests your ability to locate specific details mentioned in a reading passage. When you encounter questions asking "which of the following is mentioned," you need to scan the text for exact matches rather than making inferences.
The passage explicitly states that the Colosseum "was used for gladiatorial contests, public spectacles such as mock sea battles, animal hunts, executions, and dramas based on classical mythology." This directly confirms that mock sea battles were indeed held at the Colosseum, making choice B correct.
Let's examine why the other options are wrong. Choice A (chariot races) is not mentioned anywhere in the passage, though you might associate chariot races with ancient Rome from other knowledge. Choice C (athletic competitions like the Olympics) also doesn't appear in the text—while the passage mentions various spectacles, Olympic-style athletics aren't listed. Choice D (political debates and speeches) is similarly absent from the passage, which focuses on entertainment spectacles rather than political functions.
The key trap here is bringing in outside knowledge about ancient Rome instead of sticking strictly to what the passage states. You might know that chariot races occurred at the Circus Maximus or that Romans held athletic competitions, but this question only asks about what's explicitly mentioned regarding the Colosseum.
For detail-oriented questions like this, always return to the text and look for direct evidence. Underline or highlight the relevant sentence when you find it, then match it exactly to the answer choices without adding information from your background knowledge.
- According to the passage, what did early Mesoamerican chocolate taste like?
Answer: Bitter and spicy, often flavored with ingredients like chili.
When you encounter reading comprehension questions asking about specific details, you need to locate the exact information in the passage rather than making assumptions based on general knowledge.
The passage directly describes early Mesoamerican chocolate: "The chocolate they consumed was not the sweet treat we know today; it was a bitter, frothy beverage, often spiced with chili peppers and vanilla." This clearly indicates that the original chocolate was bitter and enhanced with spicy ingredients like chili peppers, making B the correct answer.
Let's examine why the other choices are wrong. Choice A describes chocolate as "sweet and milky," but the passage explicitly states it was "not the sweet treat we know today" and was bitter instead. Choice C suggests it was "plain and unflavored," which directly contradicts the text's mention of chili peppers and vanilla as flavorings. Choice D describes it as "nutty and savory," but there's no mention of nutty flavors, and while it may have been used ceremonially, the passage describes it as a beverage, not a broth.
Notice how the passage sets up a contrast between ancient and modern chocolate by emphasizing what the early version was not like, then describing its actual characteristics. The Spanish later added "sugar and honey to counteract the bitterness," which reinforces that the original was indeed bitter.
For HSPT reading questions, always look for direct textual evidence rather than relying on outside knowledge. When a passage contrasts past and present, pay special attention to those comparative statements—they often contain key details for questions.
- The passage mentions that the Library of Alexandria was part of a larger organization known as the...
Answer: Mouseion, a research institution dedicated to the Muses.
This question tests your ability to locate specific information directly stated in a passage. When you encounter questions asking for factual details mentioned in the text, your strategy should be to scan for the exact terms or concepts referenced in the question.
The passage explicitly states that the Library of Alexandria "was not merely a repository of documents but part of a larger research institution called the Mouseion, or 'shrine of the Muses.'" This directly answers the question, making D the correct choice. The text even provides helpful context by explaining that "Mouseion" means "shrine of the Muses," confirming this was a research institution dedicated to the Muses of Greek mythology.
Looking at the incorrect options: A mentions the Lyceum, which was indeed Aristotle's school of philosophy, but this institution is never mentioned in the passage. B references Plato's Academy, another real historical institution, but again, it doesn't appear anywhere in the text. C suggests the Ptolemaic Court, and while the passage does mention "Ptolemy II Philadelphus," it identifies him as the ruler during whose reign the Library was founded, not as the head of the larger organization that housed the Library.
The wrong answers here are classic distractors that use real historical information to test whether you're carefully reading the passage or relying on outside knowledge. On reading comprehension questions, always stick to what's explicitly stated in the text. When a question asks for a specific detail, scan for key terms rather than trying to remember the information from your general knowledge.
- What was the highest military rank Poe achieved during his initial enlistment, as mentioned in the passage?
Answer: He was promoted to Sergeant Major for Artillery.
When tackling reading comprehension questions about specific details, you need to locate the exact information in the passage and distinguish it from related but different details.
The passage clearly states that during his initial Army enlistment, Poe "rose through the ranks with remarkable speed, attaining the position of Sergeant Major for Artillery within two years—the highest non-commissioned rank achievable." This directly identifies his peak rank during that first military stint.
Let's examine why the other choices miss the mark. Choice A mentions "commissioned Second Lieutenant," but the passage never indicates Poe became a commissioned officer during his enlisted service—in fact, it emphasizes that Sergeant Major was the highest non-commissioned rank he could reach. Choice C refers to becoming "a cadet at the West Point Military Academy," but this happened after his initial enlistment ended, when he sought advancement beyond what enlisted service could offer. Choice D mentions "Corporal in his infantry division," which contradicts the passage on two counts: Poe served in Artillery (not infantry) and achieved the much higher rank of Sergeant Major (not Corporal).
The key trap here is confusing different phases of Poe's military career. The question specifically asks about his "initial enlistment," not his later time at West Point. Always pay attention to time-specific qualifiers in questions—they help you focus on the right section of the passage and avoid mixing up chronologically separate events.
- According to the passage, under what name did Edgar Allan Poe first join the U.S. Army?
Answer: He joined using the pseudonym Edgar A. Perry.
When you encounter a reading comprehension question asking for specific factual details, your task is to locate the exact information in the passage without making inferences or assumptions.
The passage directly states that in 1827, Poe "enlisted in the United States Army for a five-year term under the assumed name 'Edgar A. Perry.'" This explicit statement makes answer choice C correct—he used the pseudonym Edgar A. Perry when joining the military.
Let's examine why the other options are incorrect: Answer choice A is wrong because the passage specifically mentions he used an "assumed name," not his real name of Edgar Allan Poe. Answer choice B incorrectly suggests he used his foster father's surname and presented himself as "Edgar Allan"—this information simply isn't provided in the passage. Answer choice D is incorrect because it claims he used the alias "E. A. Perryman," but the passage clearly states the name was "Edgar A. Perry," not Perryman.
Notice that choices B and D contain plausible-sounding details that might seem historically accurate or logical, but they don't match what's actually written in the text. Choice A represents a common trap—assuming someone would use their real name when the passage explicitly states otherwise.
For HSPT reading questions, always return to the passage to verify factual details. Don't rely on outside knowledge or reasonable assumptions. The answer must be directly supported by the text, word for word, as it appears in the passage.
- What was the stated goal of the Library of Alexandria, according to the passage?
Answer: To acquire a copy of every scroll that existed in the world.
When you encounter reading comprehension questions that ask about specific details from a passage, your goal is to locate the exact information stated in the text rather than making inferences or assumptions.
The passage clearly states the Library's mission: "The Library's mandate was ambitious: to collect a copy of every known scroll in the world." This directly supports answer choice C, which correctly captures this goal of acquiring a copy of every scroll that existed in the world.
Let's examine why the other options are incorrect. Answer A suggests the Library aimed to translate works into Latin and Greek, but the passage mentions no translation activities—only collection. Answer B claims the Library focused on preserving Egyptian authors' works, which contradicts the passage's emphasis on collecting scrolls from everywhere in the world, not just Egypt. Answer D describes the Library as a public lending institution, but the passage characterizes it as a research institution (the Mouseion) rather than a public library for citizens.
The key trap here is that some answer choices sound plausible for what an ancient library might do, but they aren't supported by the actual text. Answer A might seem reasonable since many ancient works were translated between languages, and Answer D reflects our modern understanding of libraries as public institutions.
Study tip: On HSPT reading questions asking "according to the passage," stick strictly to what's explicitly stated. Don't bring in outside knowledge about what libraries typically do—focus only on what this specific passage tells you about this particular library.
- What is the primary function of passive sonar as described in the passage?
Answer: Listening for sounds without transmitting any
When you encounter reading comprehension questions about technical processes, focus on identifying the specific characteristics that distinguish different methods or types within the same system.
The passage clearly explains that passive sonar "involves simply listening for sounds made by vessels or marine animals without transmitting any sound." This directly matches answer choice D, which captures the essence of passive sonar's function: it's purely receptive, gathering information by detecting existing sounds rather than creating them.
Let's examine why the other options miss the mark. Choice A describes active sonar's method—sending out 'pings' is specifically mentioned as what active sonar does, not passive sonar. Choice B is incorrect because passive sonar doesn't calculate distances to silent objects; it can only detect objects that are already making sounds, and distance calculation requires the echo timing that only active sonar provides. Choice C is wrong because while sonar systems might be used in military communications, the passage doesn't present communication as passive sonar's primary function—it emphasizes detection and listening.
The key distinction here is between "active" (transmitting signals) and "passive" (only receiving). This mirrors a common pattern in technology where systems are categorized by whether they emit signals or simply collect existing information.
Study tip: When reading about technical systems with multiple types or categories, pay close attention to the defining characteristics that separate each type. Create a mental comparison chart as you read—this helps you avoid mixing up details between similar concepts on the test.
