Single correct option
The world's coral reefs, though they occupy less than one percent of the ocean floor, support roughly a quarter of all known marine species, making them among the most biodiverse ecosystems on the planet despite their small footprint. Rising sea temperatures, however, trigger coral bleaching, in which corals expel the algae that supply both their color and much of their nutrition, leaving them vulnerable to starvation and disease. Repeated bleaching events, occurring more frequently as oceans warm, deny reefs the recovery time they once had between stressors, pushing many toward irreversible collapse.
Which of the following best summarizes the passage?
Which of the following best summarizes the passage?
- A. Coral reefs cover very little of the ocean floor but are extraordinarily biodiverse, and shrinking recovery windows between warming-driven bleaching events threaten to push many reefs toward permanent collapse.
- B. Coral bleaching is caused by corals expelling algae, which removes their color and makes them starve.
- C. Marine biodiversity is declining across all ocean ecosystems due to rising global temperatures.
- D. Coral reefs are the most important ecosystem on Earth and must be protected at all costs.
Show answer and solution
Answer: (A) Coral reefs cover very little of the ocean floor but are extraordinarily biodiverse, and shrinking recovery windows between warming-driven bleaching events threaten to push many reefs toward permanent collapse.
The passage's core claims are: reefs are disproportionately biodiverse relative to their size, bleaching is caused by rising temperatures, and repeated bleaching (without recovery time) threatens collapse. Option A captures all three elements concisely. B describes only the mechanism of bleaching, omitting the biodiversity point and the collapse threat. C overgeneralizes beyond reefs. D is an unsupported value judgment not made in the passage.
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