Question 135·Hard·Central Ideas and Details
Marine ecologist Yuna Patel originally set out to measure how rising seawater temperatures affect reef‐building corals. Unexpectedly, her team discovered that corals from bays receiving heavy agricultural runoff showed severe bleaching at temperatures that left offshore corals unscathed. Follow-up genetic analyses revealed that the polluted bays harbored different microbial communities, which appeared to weaken the corals’ stress response. Patel argues that these findings complicate the widely held view that global warming is the singular driver of coral decline; instead, she contends, local water quality and microbial dynamics can make reefs either more vulnerable or more resilient to heat.
Which choice best states the central claim made in the passage?
For central-idea questions, restate the author’s overall conclusion in your own words—often found in the final sentence(s). Then choose the option that matches that broad claim without narrowing to a single study detail or adding unsupported explanations (like ranking causes, saying one factor is unimportant, or introducing new mechanisms such as evolution).
Hints
Use the conclusion
Focus on the last sentence: it states how Patel interprets the findings (that’s usually the central claim).
Look for a two-factor claim
The passage contrasts a “singular driver” view with an explanation that includes heat plus local water quality/microbes. Pick the option that includes both.
Avoid answers that add new causes
Be cautious of choices that introduce ideas not stated (for example, claims about coral evolution or temperature being unimportant).
Step-by-step Explanation
Identify what the question is asking
The question asks for the central claim of the passage: the author’s main point that the details and evidence are building toward.
Paraphrase the author’s conclusion
In the final sentence, Patel says her findings complicate the view that global warming is the singular driver of coral decline. She adds that local water quality and microbial dynamics can make reefs more vulnerable or more resilient to heat.
So the main idea is: heat matters, but local conditions (including microbes affected by runoff) can intensify or reduce heat’s effects.
Eliminate choices that are too narrow or that contradict the author’s emphasis
Compare each choice to the passage’s overall claim.
- Choice 1 focuses specifically on runoff-altered microbes lowering the bleaching temperature. That’s supported as a finding, but it’s too narrow to be the overall central claim because Patel’s conclusion is broader (heat + local conditions).
- Choice 3 downplays temperature by making it “only a secondary role,” which goes beyond the passage. Patel challenges the singular-driver view but still treats heat as important.
- Choice 4 introduces genetic adaptation of offshore corals, which the passage does not claim; the genetic work described concerns microbial communities in polluted bays, not offshore corals evolving heat tolerance.
Select the choice that matches the passage’s main claim
Choice 2 is the only option broad enough and accurate enough to capture Patel’s conclusion: bleaching severity depends on the interaction of rising temperatures and local environmental factors (like water quality and microbes).
Correct answer: Both rising temperatures and local environmental conditions interact to determine how severely corals bleach.