Which of the following reasons caused catastrophic coral bleaching and mass coral deaths in the Andaman and Nicobar Islands?Select the correct answer from the code given below:

1. A

   Increased industrial activities in the coastal regions

   Option (a) claims that increased industrial activities in the coastal regions caused catastrophic coral bleaching. However, localized industrial pollution alone was not the primary driver of this widespread ecological disaster in the remote islands.

2. B

   Increase of 2°C temperature in the Indian Ocean

   Option (b) claims that an increase of 2°C temperature in the Indian Ocean caused catastrophic coral bleaching and mass coral deaths in the Andaman and Nicobar Islands. This option is the key because severe marine heatwaves and sustained thermal stress of this magnitude are scientifically proven to trigger massive expulsion of zooxanthellae by corals, leading to widespread bleaching and subsequent mortality across the reef ecosystems.

3. C

   Heavy marine pollution

   Option (c) claims that heavy marine pollution was the root cause of the mass coral deaths. While pollution degrades water quality, it was thermal anomaly rather than general pollution that precipitated this specific catastrophic bleaching event.

4. D

   Decrease of temperature by 4°C in the Indian Ocean

   Option (d) claims a decrease of temperature by 4°C in the Indian Ocean caused the devastation. Corals are extremely sensitive to warming rather than sudden unnatural cooling of such large proportions, making this option factually incorrect.

Summary. Official key is (b) because an increase of 2°C temperature in the Indian Ocean led to severe marine heatwaves that triggered the catastrophic coral bleaching and mass mortality in the Andaman and Nicobar Islands. Options (a) and (c) incorrectly blame localized industrial activities and heavy marine pollution instead of the documented thermal anomalies. Option (d) erroneously suggests a large temperature decrease, whereas tropical corals suffer primarily from sustained ocean warming and thermal stress. Thus, option (b) correctly identifies the exact environmental factor responsible for the ecological collapse.