The correct answer is option 1: Sundarbans. Sundarbans is not only the largest mangrove forest in India but also in the world. Mangrove forests are unique coastal ecosystems that are characterized by the presence of salt-tolerant trees and shrubs. They are found in tropical and subtropical regions.

Option 2: Coringa East is not the correct answer. Coringa East is a mangrove forest located in the Godavari delta of Andhra Pradesh, India. While it is a significant mangrove forest in India, it is not the largest in the world.

Option 3: Muthupet is not the correct answer. Muthupet is a smaller mangrove forest located in Tamil Nadu, India. It is not as large as the Sundarbans.

Option 4: Malvan is not the correct answer. Malvan is not a mangrove forest. It is a town in Maharashtra, India.

Therefore, the correct answer is option 1: Sundarbans, which is the largest mangrove forest in India and in the world.