The correct answer for this question is option 3, Andaman and Nicobar Islands. Coral reefs are one of the most important marine ecosystems, and Andaman and Nicobar Islands have the largest area of coral reefs in India.

Option 1, Gujarat, does not have a significant area of coral reefs compared to other options.

Option 2, Tamil Nadu, also has coral reefs, but the area is not as extensive as in Andaman and Nicobar Islands.

Option 4, Lakshadweep, is known for its coral reefs, but the area is not as large as in Andaman and Nicobar Islands.

Therefore, it can be concluded that Andaman and Nicobar Islands have the largest area under coral reefs in India.