Coral reefs are sometimes called "rainforests of the sea" because of their extraordinary biodiversity, yet they cover less than one percent of the ocean floor. As ocean temperatures rise, corals expel the symbiotic algae that give them color and energy — a process called bleaching. Repeated bleaching events, marine biologists warn, could collapse reef ecosystems within decades, with cascading effects on the species that depend on them.
Which choice best states the main idea of the text?
- A
Less than one percent of the ocean floor is covered by reefs.
- Bcheck_circle
Rising ocean temperatures threaten coral reefs and the ecosystems they support.
- C
Rainforests and coral reefs are equally biodiverse.
- D
Coral reefs are colorful because of symbiotic algae.
Explanation
The passage moves from describing reefs to warning about temperature-driven collapse — C. A, B, and D are supporting details, not the central claim.