The correct answer is: a) Coral reefs.
The Gulf of Mannar is a shallow sea between India and Sri Lanka. It is known for its coral reefs, which are home to a variety of marine life. The reefs are also important for tourism and fisheries.
Seagrass meadows are underwater meadows of seagrasses. They are found in shallow, coastal waters and provide important habitat for fish and other marine life.
Kelp forests are underwater forests of kelp, a type of seaweed. They are found in cold, nutrient-rich waters and provide important habitat for fish and other marine life.
Salt marshes are coastal wetlands that are dominated by salt-tolerant plants. They are found in areas where the land meets the sea and are important for water filtration and wildlife habitat.