The Gulf of Mannar Marine National Park is known for protecting:

Coral reefs and marine life
Mangroves
Coastal birds
Estuarine crocodiles

The correct answer is: a) Coral reefs and marine life.

The Gulf of Mannar Marine National Park is a protected area in the Gulf of Mannar, off the southeastern coast of India. It is the first marine national park in India and is known for its coral reefs and marine life. The park is home to over 300 species of coral and over 5,000 species of fish. It is also home to a variety of other marine life, including turtles, dolphins, and dugongs.

Mangroves are a type of tree that grows in tropical and subtropical coastal areas. They are important for protecting coastlines from erosion and providing a habitat for a variety of marine life. Coastal birds are birds that live near the coast. They include a variety of species, such as gulls, terns, and pelicans. Estuarine crocodiles are a type of crocodile that lives in estuaries, which are areas where rivers meet the ocean. They are found in tropical and subtropical regions around the world.

The Gulf of Mannar Marine National Park is an important area for conservation. It is home to a variety of marine life, including coral reefs, fish, turtles, dolphins, and dugongs. The park is also important for protecting the coastline from erosion.