The correct answer is (d), Gulf of Mannar.
The Gulf of Mannar is a marine national park located in the Indian state of Tamil Nadu. It is the first marine national park in India and was established in 1986. The park covers an area of 10,000 square kilometers and is home to a variety of marine life, including coral reefs, sea turtles, dolphins, and dugongs.
The Gulf of Mannar is also an important fishing ground and is home to a number of traditional fishing communities. The park is managed by the Tamil Nadu Forest Department and is open to the public for tourism.
The other options are incorrect because they are not marine national parks.
(a) Bhitar-Kanika is a wildlife sanctuary located in the Indian state of Odisha.
(b) Sundarban is a mangrove forest located in the Indian state of West Bengal and the Bangladesh Sundarbans.
(c) Gahirmatha is a national park located in the Indian state of Odisha. It is home to the world’s largest population of Olive Ridley sea turtles.