Complete Guide to TOEFL Reading Rhetorical Purpose Questions
What Are Rhetorical Purpose Questions?
Rhetorical Purpose questions test your ability to understand why an author includes specific information in a reading passage. These questions go beyond basic comprehension and focus on the function of a sentence, phrase, or example within the overall structure and meaning of the text. Instead of asking what the author says, they ask why the author says it in a particular place or way.
You may be asked, for example, why the author includes a certain comparison, provides a particular detail, or quotes another person. To answer correctly, you need to think about how that information connects to the main point of the paragraph or the larger argument in the passage. Sometimes the purpose is to support a claim, provide clarification, highlight a contrast, or illustrate a broader idea.
In many cases, it is not enough to read only the sentence mentioned in the question. You may need to read the sentence before or after it—or even return to the beginning of the paragraph or passage—to fully understand how the information fits in. This type of question often depends on seeing relationships between ideas, such as cause and effect, general and specific, or claim and evidence.
Rhetorical Purpose questions can appear in different formats, such as:
- Why does the author include the information about X?
- What is the function of the example in paragraph 2?
- In the context of the passage, why is X mentioned?
To succeed on these questions, focus on how ideas are organized and connected. Pay close attention to transition words like “for instance,” “on the other hand,” or “this suggests,” as they can give strong clues about the author’s intent. Above all, remember that the correct answer is not just about what the author says, but about what purpose that information serves in the passage.
How To Understand The Author's Intention
Question 1
Paragraph: It is now well established that petroleum migrates through aquifers and can become trapped in reservoirs. Petroleum migration is analogous to groundwater migration. When oil and gas are squeezed out of the shale in which they originated and enter a body of sandstone or limestone somewhere above, they migrate readily because sandstones (consisting of quartz grains) and limestones (consisting of carbonate minerals) are much more permeable than any shale. The force of molecular attraction between oil and quartz or carbonate minerals is weaker than that between water and quartz or carbonate minerals. Hence, because oil and water do not mix, water remains fastened to the quartz or carbonate grains, while oil occupies the central parts of the larger openings in the porous sandstone or limestone. Because oil is lighter than water, it tends to glide upward past the carbonate- and quartz-held water. In this way, oil becomes segregated from the water; when it encounters a trap, it can form a pool.
Question: Why does the author mention “The force of molecular attraction between oil and quartz or carbonate minerals is weaker than that between water and quartz or carbonate minerals”?
A. To suggest that oil is chemically more compatible with quartz than with shale
B. To explain why oil can move more freely than water through sandstone or limestone
C. To highlight a reason why oil and water can form stable mixtures in certain environments
D. To show that oil is more strongly bonded to mineral surfaces than water is
Explanation
Question 2
Paragraph: How much oil is there in the world? This is an extremely controversial question. Many billions of barrels of oil have already been pumped out of the ground. A lot of additional oil has been located by drilling but is still waiting to be pumped out. Possibly a great deal more oil remains to be found by drilling. Unlike coal, the volume of which can be accurately estimated, the volume of undiscovered oil can only be guessed at. Guesses involve the use of accumulated experience from a century of drilling. Knowing how much oil has been found in an intensively drilled area, such as eastern Texas, experts make estimates of probable volumes in other regions where rock types and structures are similar to those in eastern Texas. Using this approach and considering all the sedimentary basins of the world, experts estimate that somewhere between 1,500 and 3,000 billion barrels of oil will eventually be discovered.
Question: Why does the author mention eastern Texas in paragraph 5?
A. To provide an example of a region where oil has been found but not yet extracted
B. To illustrate how expert predictions about geology have proven accurate
C. To identify a place where oil reserves are still largely unknown
D. To give an example of an area that has been thoroughly explored for oil
Explanation
This question tests your ability to identify the rhetorical purpose of a specific detail within the paragraph. The mention of “eastern Texas” is not included just to name a place; it serves a particular role in clarifying how experts estimate oil volumes in less explored regions.
The key point of the paragraph is to explain the method experts use to predict undiscovered oil by comparing it to areas with extensive drilling data. The mention of eastern Texas provides a concrete example of such a well-studied region. By referencing eastern Texas, the author helps readers understand that expert estimates rely on detailed knowledge from intensively drilled areas and apply that knowledge to other regions with similar geological features.
The phrase “such as” is important here. It signals that eastern Texas is an example illustrating the general idea just mentioned. When you see words like “such as,” “for example,” or “including” in a passage, they often mean the author is giving an example to help explain something more clearly.
In simpler terms, think of it like this: the author is saying, “We know a lot about places like eastern Texas because they have been studied carefully. So, we use what we learn there to guess how much oil might be in other places that look similar.” The example makes the explanation easier to understand by showing a real place where this happens.
This is a common strategy in TOEFL reading passages. Authors often use examples to make complicated ideas clearer or to support their main points. When answering rhetorical purpose questions, looking for signal words like “such as” can help you find why the author included a detail or example.
Answer choice D correctly shows that eastern Texas is mentioned because it is a place where intensive oil exploration has already occurred. This fits the author’s purpose of explaining how experts use data from well-known regions to estimate oil in other areas.
Question 3
Paragraph: It is believed that the facial pits, or pit organs, located on the heads of some snakes function as specialized receptors for infrared (heat) radiation. When a rattlesnake strikes, it appears that the direction of the strike is determined by detecting infrared radiation emitted by its prey. Interestingly, a rattlesnake only targets warm-blooded prey, and if the prey is at room temperature, the snake will not strike. However, a blindfolded snake will accurately strike at a dead rat that is warmer than its surroundings when it is pulled across the cage. Since the snake cannot rely on vision due to the blindfold, and still strikes accurately at objects like a moving, cloth-wrapped electric bulb, it is evident that the pit organs are responsible for detecting the heat of warm objects. All snakes with pit organs prefer to feed on warm-blooded prey, further supporting the belief that these organs function as infrared detectors. In rattlesnakes, the pit organs are positioned between the nostrils and eyes, one on each side, and are connected to numerous nerves, suggesting a sensory role for these organs.
Question: Why does the author mention a “cloth-wrapped electric bulb” in the passage?
A. To illustrate the size of prey usually attacked by snakes
B. To explain how scientists were able to trick blindfolded snakes
C. To eliminate the possibility that snakes locate prey by using a sense of smell
D. To prove that blindfolded snakes will strike more often at a dead rat than an electric bulb
Explanation
The mention of the cloth-wrapped electric bulb also serves as a good example of how scientists use controlled experiments to test specific ideas. In this case, researchers wanted to determine how blindfolded snakes could still strike at prey. To isolate the variable of heat, they used a non-living object—the bulb—wrapped in cloth and warmed up to simulate the body temperature of real prey. By keeping everything else the same and only changing the presence of heat, they could clearly observe whether the snake was responding specifically to temperature.
This is a key feature of scientific investigation: when researchers want to test a hypothesis, they try to keep all conditions the same except for one variable. Here, the only meaningful difference was the heat emitted by the bulb. The fact that the snake still struck at the bulb, despite its unusual shape, lack of smell, and lack of life, allowed scientists to conclude that heat alone was enough to trigger the strike. This strengthens the argument that the pit organs are specialized for detecting infrared radiation and not other cues like movement, smell, or shape.
So, the cloth-wrapped bulb is more than just a strange example. It’s a carefully chosen tool in a controlled experiment that lets scientists isolate and test one factor at a time. This method helps ensure that their conclusions are based on reliable evidence, not guesswork.
TOEFL Rhetorical Purpose Questions Quiz [Free Sample]
This premium quiz focuses on TOEFL Reading Rhetorical Purpose questions. These items test your ability to understand why a particular sentence or detail is included in the passage—not just what it says. You’ll be asked to think about how a sentence functions in context, whether it introduces a key idea, provides evidence, explains a cause, or connects two parts of the argument. Each passage and question in this set closely follows the tone, logic, and difficulty level of official TOEFL materials. The explanations highlight how TOEFL often uses signal words, structural clues, and paragraph flow to test your reasoning.
A free sample is included so you can try it out before committing to the full set. For more practice with other question types, you can also check out our free 100-question Sentence Insertion quiz, or explore our breakdown of TOEFL Sentence Simplification questions, which are covered in a separate guide.
TOEFL Rhetorical Purpose Questions Quiz [Premium]
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