Consider the following statements 1) Most of the world's coral reefs are in tropical waters. 2) More than one-third of the world's coral reefs are located in the territories of Australia, Indonesia and Philippines. 3) Coral reefs host far more number of animal phyla than those hosted by tropical rainforests. Which of the statements given above is/are correct?

All three statements hold, so D is correct. The core concept is the geography and biology of coral reefs, which are built by colonial stony corals and their symbiotic algae (zooxanthellae).

• Statement 1 is correct. Reefs need warm water (roughly 20 to 28 degrees C), clear light and salinity near normal. That confines most reefs to tropical waters between about 30 degrees N and 30 degrees S.
• Statement 2 is correct. Indonesia has the largest share of the world's reefs, with Australia (Great Barrier Reef) and the Philippines close behind. Together they hold more than a third of the total, which is why the Coral Triangle is a priority for conservation.
• Statement 3 is correct. Reefs host about 32 of the 33 animal phyla, a remarkable spread for a marine habitat. Rainforests are rich in species but have far fewer phyla. Aspirants often confuse species richness with phylum richness.

Mains link: bleaching from marine heatwaves, ocean acidification and coastal livelihoods make reefs a standard topic under climate change, biodiversity and the blue economy. Recent mass bleaching events (2016 to 2024) have made reef loss a current affairs issue.

Trap: doubting statement 3 because rainforests are the famous biodiversity hotspots, when the question is about the number of animal phyla, not species.