Read the passage: A coral reef is a large underwater structure made of living and dead corals. These reefs form in tropical seas between 30° north and south of the equator, where they shelter many fish and other animals. Most present-day reefs grew after the last ice age, when rising seas flooded the continental shelves and coral communities built reefs upward as the water rose. Because corals need warm, sunlit water, they grow near the surface, which makes them vulnerable to human activity. Pollution from boats and coastal building clouds the water and cuts sunlight; toxic substances can bleach and kill corals. Many countries now restrict construction near reefs and regulate shipping to protect them. Which best states the main idea of the passage?
ACoral reefs grew after the last ice age
BCoral reefs are found only near the equator
CShips frequently collide with coral reefs
DCoral reefs are valuable but fragile ecosystems under threat from human activity
Answer & Solution
Correct answer: D. Coral reefs are valuable but fragile ecosystems under threat from human activity
The passage describes what reefs are, how they form, and the threats they face plus protection — the overarching idea is their value and fragility. The other options are supporting details, not the main idea.
Related questions
Read the passage:
The water cycle describes the continuous movement of water through EartRead the passage:
The water cycle describes the continuous movement of water through EartRead the passage:
The water cycle describes the continuous movement of water through EartRead the passage:
The water cycle describes the continuous movement of water through EartRead the passage:
A coral reef is a large underwater structure made of living and dead coRead the passage:
A coral reef is a large underwater structure made of living and dead coRead the passage:
A coral reef is a large underwater structure made of living and dead coIn the passage, the word 'SAVOURING' (as in 'savouring the freedom') means: