Answer: A
Correct answer: the Sundarbans and the coastal deltas
Mangroves grow in the intertidal zone where fresh and salt water mix, so they are confined to sheltered coasts, deltas and estuaries. In India the largest by far is the Sundarbans in the Ganga–Brahmaputra delta, with further stands in the Mahanadi, Godavari and Krishna deltas, the Gulf of Kutch, the Andaman and Nicobar Islands and parts of Kerala. They are the only trees that tolerate regular immersion in salt water, managing it by excluding salt at the roots, excreting it through the leaves, or both. Their stilt roots anchor them in soft mud and their vertical pneumatophores take in the oxygen the waterlogged sediment cannot supply. Their practical value is out of proportion to their area: they are nurseries for fish and prawns, they absorb cyclone storm surge and check coastal erosion, and they store carbon exceptionally efficiently. Their protective role was widely noted after the 2004 tsunami, when settlements behind intact mangrove belts suffered far less.