According to the passage, what do coral polyps produce?
Coral reefs are built by tiny animals called polyps, which secrete a hard skeleton of calcium carbonate. Over many generations the skeletons of dead polyps accumulate and form the structure of the reef. Reef-building corals live in partnership with microscopic algae that live inside their tissues. The algae use sunlight to make food and share it with the coral, which is why reefs are found mostly in shallow, clear water where sunlight can penetrate. This partnership is sensitive to temperature: if the water becomes too warm, the corals expel their algae and turn white, a process called bleaching. Although bleached corals can recover if conditions improve, prolonged stress can kill them. Because reefs shelter about a quarter of all marine species, their loss would have effects far beyond the coral itself.
Answer and explanation
Correct answer: A. A hard skeleton of calcium carbonate
- Step 1: The passage says polyps secrete a skeleton. Step 2. It is made of calcium carbonate. Answer: a hard skeleton. Why not the others: the algae live in the coral and are not produced by it.
Practise more Academic Passages (Set 2).
Free questions with an explanation for every one, and full timed TOEFL mock tests.
More Academic Passages (Set 2) questions
- What is the passage mainly about?
- According to the passage, what does the length of the waggling run indicate?
- The word 'sophisticated' in the passage is closest in meaning to:
- Why did the researchers move the food sources to new places?
- Which of the following can be inferred from the passage?
- Why are reefs found mostly in shallow, clear water?