Text Structure and Purpose

Explanation

Text Structure and Purpose questions ask you to step back from the details of a passage and see how it is built and why. They come in three related forms. Main-purpose items ask, “Which choice best describes the main purpose of the text?”; the right answer captures the author’s overall aim—to describe, explain, argue, convey, or illustrate something—without fixating on one detail. Overall-structure items ask how the parts are arranged, and the correct choice names the pattern the whole text follows (for example, introducing a trend and then noting a drawback, or presenting an assumption and then complicating it).

Function items ask what job a specific part does—a sentence, an opening question, or an underlined portion—within the text as a whole; the right answer explains how that piece contributes to the passage, not merely what it says. In every form, the correct answer must fit the entire passage: it cannot be too narrow (true of only one part), too broad (claiming more than the text does), or a plausible idea the text never actually carries out.

Example 1

For years, city planners assumed that widening a congested highway would ease its traffic. Transportation researcher Dana Ruiz studied a dozen highways that had been widened and found the opposite: within a few years each was as clogged as before, because the extra lanes drew in drivers who had previously avoided the route. Ruiz argues that cities hoping to reduce congestion should invest in public transit rather than in ever-wider roads.

Which choice best describes the main purpose of the text?

To compare the cost of widening highways with the cost of building public transit

To present a common assumption about traffic and the research that undercuts it

To describe the daily experience of drivers on a congested highway

To trace the history of highway construction in a particular city

Choice B is the best answer. The text opens with the common assumption that widening a highway eases traffic, then presents Ruiz’s finding that widened highways clog again, undercutting that assumption. Choice A is incorrect because the text does not compare the costs of the two approaches. Choice C is incorrect because it names a detail (congestion) rather than the author’s overall aim. Choice D is incorrect because the text discusses a research finding, not the history of a city’s highway construction.

Example 2

Coral reefs are among the most crowded habitats on Earth. Marine biologist Sole Okafor wondered how so many fish species avoid competing for the same food. Tracking dozens of species on a single reef, she found that closely related fish feed at slightly different times of day and in slightly different zones of the reef. These small separations, she concluded, let many species share one reef without driving one another out.

Which choice best describes the function of the second sentence in the text as a whole?

It presents the study’s main finding about how fish divide the reef.

It poses the question that the research described in the text sets out to answer.

It defines a term used later in the text.

It concedes a weakness in the researcher’s method.

Choice B is the best answer. The second sentence raises the question Okafor investigates—how so many species avoid competing—which the rest of the text answers. Choice A is incorrect because the finding appears in the later sentences, not the second. Choice C is incorrect because the sentence defines no term. Choice D is incorrect because it acknowledges no flaw in the method; it sets up the inquiry.

Tips for solving

Decide which kind of question you have: overall purpose, overall structure, or the function of one part. Each calls for a different kind of answer.
Example: A passage describes a new carbon-capture technology, outlines a recent field trial, and notes potential economic barriers to widespread deployment.
- Question A (Overall Purpose): "Which choice best describes the main purpose of the text?" (Target: Focus on the author's overarching goal—e.g., to present a new technology and evaluate its feasibility).
- Question B (Overall Structure): "Which choice best describes the overall structure of the text?" (Target: Focus on the sequence of ideas—e.g., an innovation is introduced, an experiment is detailed, and a practical challenge is noted).
- Question C (Function of One Part): "Which choice best states the function of the underlined sentence in the text as a whole?" (Target: Focus strictly on the job of that specific sentence—e.g., it highlights a limitation of the technology).
For purpose questions, state the author’s aim in your own words first (to describe? explain? argue? convey?), then match it to a choice.
Example: A text details how certain deep-sea octopus species alter their skin pigments to match surrounding coral, citing specific observations from marine biologists.
- Your Aim Prediction: "The author wants to explain how deep-sea octopuses use camouflage and provide examples from research."
- Matching Choice: to describe a specific adaptive behavior in marine organisms and present evidence of its occurrence.
For structure questions, map the passage in parts—what does the beginning do, then the middle, then the end?—and find the choice whose pattern fits the whole.
Example: A passage opens by mentioning a long-held belief that birds are sole descendants of one specific dinosaur group. It then presents recent fossil findings that challenge this view. It ends by proposing a revised classification system.
- Passage Map:
  - Beginning: Establishes a traditional scientific view.
  - Middle: Introduces new evidence that contradicts that view.
  - End: Offers a new model based on the evidence.
For function questions, ask what job the named sentence does for the passage (it introduces, defines, qualifies, exemplifies, concludes), not merely what it says.
Example: A passage argues that urban rooftop gardens lower city temperatures. The underlined sentence states: "For instance, a 2021 study in Chicago found that ambient temperatures dropped by 3°F near rooftop vegetation."
- What it says: A Chicago study showed a 3°F temperature drop near rooftop gardens.
- What job it DOES (Function): It provides a concrete example (exemplifies) to support the general claim made in the preceding sentence.
- Correct Choice: It offers empirical evidence to illustrate a general claim made earlier in the passage.
Reject choices that are true of only one part of the text (too narrow) or that claim more than the text supports (too broad).
Example: A passage discusses the discovery of a 3,000-year-old trade route in the Andes, noting the types of pottery found along the path and concluding that regional trade networks were more extensive than previously thought.
- Too Narrow Trap Choice: to detail the specific decorative patterns found on ancient Andean pottery. (Captures only one small detail mentioned in the middle).
- Too Broad Trap Choice: to provide a comprehensive history of trade across ancient South America. (Claims far more than the passage's focus on one specific route).
- Correct Choice: to describe a recent archaeological discovery and explain its implications for understanding ancient trade networks.
Watch for choices that describe something the text never does—comparing, criticizing, predicting, recommending—even if they sound reasonable.
Example: A passage objectively explains how tree rings are used by scientists to measure historical climate patterns.
- Unperformed Action Trap Choice: to criticize traditional methods of climate data collection and recommend a superior alternative. (The passage explains a method objectively; it never criticizes or recommends).
- Correct Choice: to explain how a specific natural phenomenon is utilized to study past environmental conditions.
On the hardest items, distractors are often half-right: they capture part of the passage but misstate the role of the part in question. Confirm every word of the choice against the text.
Example: A text describes a new satellite system that tracks deforestation. The underlined sentence mentions that previous ground-based tracking methods took months to deliver data.
- Half-Right Trap Choice: It introduces a new satellite system that replaces outdated environmental tracking methods. (Describes the passage generally, but misstates the function of the underlined sentence, which was to contrast speed, not introduce the satellite).
- Correct Choice: It provides a contrast to highlight the speed advantage of the system described in the passage.

Practice questions

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Question 1 · easy

Most bicycle tires go flat when a sharp object punctures the rubber and the pressurized air rushes out. Engineer Priya Nair and her team have developed a new kind of tire filled not with air but with a soft, honeycomb-shaped plastic lattice that supports the rider’s weight. Because the lattice contains no pressurized air, a nail or shard of glass that would ruin an ordinary tire simply passes through the open cells without causing any lasting damage, allowing the rider to continue on without stopping to make a repair. In tests on debris-strewn city streets, the lattice tires rolled for thousands of miles without a single flat.

Which choice best states the main purpose of the text?

Question 2 · easy

Bioluminescence is the production of light by a living organism through a chemical reaction inside its body. Many deep-sea fish rely on this ability to survive in waters that sunlight never reaches. Biologist Tomás Herrera has shown that the anglerfish uses a glowing lure, dangling from a stalk above its mouth, to draw small, curious prey close enough to be swallowed. Other fish, he notes, use their light instead to startle approaching predators or to signal potential mates in the surrounding darkness. Because sunlight fades to blackness a few hundred meters down, this self-made light is often the only illumination these creatures ever encounter.

Which choice best describes the function of the first sentence in the text as a whole?

Question 3 · easy

In the early 1900s, the inventor Garrett Morgan noticed that the traffic signals of his day showed only “stop” and “go,” giving drivers no warning that a change was about to occur, and collisions were frequent at busy intersections. In 1923 Morgan patented an improved signal that added a third position to warn drivers that the light was about to change, allowing them time to slow down safely. Versions of his warning signal were soon adopted in cities across the country and influenced the design of the modern traffic light. Morgan, already known for inventing an early breathing hood for firefighters, later sold the rights to his signal to a large company.

Which choice best states the main purpose of the text?

Question 4 · easy

Some plants defend themselves against hungry insects by releasing chemicals into the air when their leaves are bitten. Scientists once assumed that these airborne signals served only to repel the attacking insects directly. More recent work suggests a second role: the chemicals can also travel to a plant’s own undamaged leaves and to neighboring plants, prompting them to strengthen their defenses before any attack reaches them. For instance, a bean plant exposed to the scent of a bitten neighbor begins producing bitter compounds that make its leaves harder for insects to digest.

Which choice best describes the function of the final sentence in the text as a whole?

Question 5 · easy

More and more restaurants now let customers order and pay through an app on their phones instead of speaking with a server. For customers, the appeal is clear: they can browse the menu at their own pace, split the bill easily, and avoid waiting to flag someone down. Restaurants benefit too, since staff can serve more tables at once. Yet the shift also carries a cost, because some diners miss the friendly guidance of a server, and older customers unfamiliar with the technology can feel excluded and frustrated. A few restaurants have responded by keeping a handful of servers on hand for guests who would rather order the traditional way.

Which choice best describes the overall structure of the text?

Question 6 · easy

The following text is adapted from a 1906 short story. Elena has returned to the seaside town where she spent her childhood summers. The moment the salt wind touched her face, the years fell away. She knew, without looking, the cry of the gulls over the harbor and the particular gray of the water under a clouded sky. Every shuttered shopfront and worn stone step seemed to lean toward her in greeting. She walked more slowly than she needed to, unwilling to let a single familiar corner pass by unnoticed. At the harbor wall she paused and felt, for the first time in years, that she had truly come home.

Which choice best states the main purpose of the text?

Question 7 · easy

For decades, farmers have battled a fungus that rots the roots of banana plants and can destroy an entire plantation. A team led by botanist Wei Chen has now bred a banana variety whose roots release a natural compound that keeps the fungus from taking hold. In field trials, plots planted with the new variety remained healthy while nearby plots of the usual variety withered. If the results hold, the discovery could protect a fruit that millions of people around the world depend on for food. Chen cautions, however, that the variety must still be tested against the many strains of the fungus found in different regions.

Which choice best describes the function of the second sentence in the text as a whole?

Question 8 · easy

Every year, huge quantities of used cooking oil are thrown away by restaurants, often clogging city sewer pipes when the oil is poured down drains. Chemist Adaeze Okonkwo has developed a simple process that converts this waste oil into a clean-burning fuel suitable for trucks and buses. Several transit companies have begun collecting oil from local restaurants and running their vehicles on the resulting fuel, cutting both their fuel costs and the amount of waste sent to landfills. Okonkwo hopes the method can be adopted widely by cities around the world.

Which choice best describes the main purpose of the text?

Question 9 · easy

Archaeologists have uncovered a 3,000-year-old workshop in southern Spain where craftspeople shaped tools and ornaments from ivory. Chemical analysis of the ivory has now revealed a surprise: much of it came from elephants living in Africa, hundreds of miles across the sea. Before this discovery, researchers had assumed that the community obtained its ivory only from nearby animals and had little contact with distant lands. The new evidence suggests instead that the settlement took part in long-distance trade networks far earlier than anyone had thought. Similar analyses of ivory from other early sites may soon reveal how far these ancient trade routes actually reached.

Which choice best describes the function of the third sentence in the text as a whole?

Question 10 · easy

Using a network of underwater microphones, marine biologist Lena Fischer recorded the calls of a small population of whales off the coast of Norway. When she compared the recordings with those made by other researchers near Iceland, she found that the two groups produced strikingly different patterns of sound. This finding provides the first clear evidence that these whales, long assumed to share a single call, in fact maintain distinct regional dialects, and it opens a new way of tracking separate populations as they move through the ocean. Fischer now plans to place more microphones along the coast to learn how many distinct dialects the region’s whales use.

Which choice best describes the overall structure of the text?

Question 11 · easy

Honey is one of the very few foods that essentially never spoils. Scientists explain this remarkable staying power by pointing to honey’s unusual chemistry: it contains very little water and is naturally acidic, two conditions in which the bacteria and molds that ruin most other foods simply cannot grow. Bees further add an enzyme that produces small amounts of hydrogen peroxide as the honey slowly ripens, killing off any stray microbes that might otherwise survive. Archaeologists exploring ancient Egyptian tombs, for instance, have discovered sealed jars of honey more than three thousand years old that remain perfectly edible today. Because of these combined qualities, honey has been prized as both a food and a natural preservative since ancient times.