Method: this is a find-out question, so build the answer in three parts — (i) what kind of landform it is and how it formed, (ii) what makes it different from every other delta, (iii) what a visitor actually goes there to see. Use an atlas for the location, and the chapter's own section on deltas (page 24) for the geography.
What a good answer must contain: the rivers that built it and the sea it opens into; the fact that it is shared between India (West Bengal) and Bangladesh; the mangrove forest and why mangroves grow there and not elsewhere; the Royal Bengal tiger; its recognition as a protected area; the livelihoods it supports; and the hazards it faces.
Sample answer:
The Sundarbans is the delta built where the Ganga, Brahmaputra and Meghna meet the Bay of Bengal. It is the largest delta in the world, and it is shared between West Bengal in India and Bangladesh. As Fig. 2.13 shows, the rivers here split into a maze of distributaries that wind between hundreds of low, muddy islands — exactly the fan-shaped, sediment-built landform described on page 24.
What makes it unique is that it is not farmland but forest — the largest mangrove forest on Earth. Mangroves are trees that can live with their roots in salt water, and they send up breathing roots through the mud. They can grow here because a delta gives them what nothing else does: soft new sediment, shallow water, and the daily mixing of river water with sea water. The name Sundarbans is usually traced to the sundari tree that grows there.
Tourists come for the wildlife and the waterways. The Sundarbans is the only mangrove forest in the world with a population of Royal Bengal tigers, which are famous for swimming between the islands. Visitors also see estuarine crocodiles, spotted deer, snakes and a great variety of birds. Because there are no roads between the islands, the whole visit is made by boat through narrow creeks — an experience found nowhere else. It is a national park and a protected biosphere, which is itself a draw.
The delta also shows both sides of what page 24 says about deltas. It gives fertile land, fishing, honey collection and boat transport to the people who live there — and it is very prone to flooding, cyclones and the erosion of its islands, so life on it is never secure.