Question 85·Easy·Text Structure and Purpose
Marine biologists studying coral reefs have observed that some coral species are coping with rising ocean temperatures by forming new partnerships with heat-tolerant algae, increasing their chances of survival. Until recently, most researchers assumed that corals could host only a single species of algae throughout their lives, but the new findings suggest that the symbiotic relationship is more flexible than previously believed.
Which choice best describes the function of the underlined portion in the text as a whole?
For function/purpose questions, first briefly summarize the passage and then ask: “What is this specific part doing in the author’s argument?” Pay close attention to signal words like "Until recently", "but", "however", or "therefore", because they show whether the underlined portion is giving background, contrasting an idea, providing evidence, or drawing a conclusion. After you decide its role in simple terms (for example, "explains old belief" or "shows result"), eliminate any choices that don’t match that role exactly, especially answers that describe evidence, doubt, or hypotheses when the text is clearly just providing context.
Hints
Locate the time frame of the underlined portion
Focus on the phrase "Until recently" in the underlined part. Is it talking about something new, or something that was believed before the new findings?
Notice the contrast word "but"
Look at how the underlined portion connects to the phrase "but the new findings suggest". Does the underlined part agree with the new findings, or set up something for the new findings to challenge?
Think about purpose, not content detail
Ask yourself: Is the underlined statement giving old beliefs, new evidence, a challenge, or a testable idea? Then choose the option that best describes that role in the whole text.
Step-by-step Explanation
Understand what the passage is saying overall
First, summarize the whole text in your own words.
- Marine biologists have recently observed that some corals can cope with warming oceans by forming new partnerships with different, heat-tolerant algae.
- The underlined portion then says that until recently, most researchers thought corals could host only one species of algae for life.
- The sentence then continues with "but the new findings" showing the relationship is more flexible.
So the structure is: new observation, then past belief, then contrast with new findings.
Identify what the underlined portion actually does
Look closely at the underlined part: "Until recently, most researchers assumed that corals could host only a single species of algae throughout their lives".
Ask: Is this something new the scientists just discovered now, or is it describing what people used to think?
- The phrase "Until recently" tells you this is about earlier assumptions.
- It describes what "most researchers assumed" in the past.
So the underlined portion is giving past belief / background information, not the new result.
Connect the underlined portion to the rest of the text
Now think about how that past belief affects how we view the new findings.
- The first sentence: new observations that corals can form new partnerships with heat-tolerant algae.
- Underlined portion: past belief that corals could host only one species of algae for life.
- Then: "but the new findings suggest" that the symbiosis is more flexible than previously believed.
This contrast shows why the new findings matter: they challenge what researchers used to think and therefore are surprising and important.
Match that role to the best choice
Now compare this role to each answer choice:
- It does not question the new observations (it just reports an old belief), so choice A is wrong.
- It is not evidence for the new conclusion (it is what was believed before the new evidence), so choice B is wrong.
- It is not a hypothesis to be tested in the rest of the sentence (the rest of the sentence actually disagrees with it), so choice D is wrong.
The only answer that matches is that the underlined portion gives past background about researchers' earlier assumptions, which makes the recent observations seem more surprising. So the correct answer is: “It supplies historical context that underscores why the recent observations are surprising.” (choice C).