Which of the following National Parks is unique in being a swamp with floating vegetation that supports a rich biodiversity?

The correct answer is B) Keibul Lamjao National Park. It lies in Manipur on Loktak Lake and is the world's only floating national park. Its floating mats of vegetation, locally called phumdis, are heaped organic matter, soil and vegetation at various stages of decomposition. Many species depend on them, including the endangered sangai deer, the Manipur brow-antlered deer, which is found nowhere else in the wild.

Why the others are wrong:

• Bhitarkanika (Odisha): famous for mangroves and estuarine crocodiles in the Brahmani-Baitarani delta. It has no floating vegetation.
• Keoladeo Ghana (Rajasthan): a freshwater wetland and bird sanctuary at Bharatpur, a Ramsar site, known for wintering waterbirds. Its vegetation is not floating.
• Sultanpur (Haryana): a wetland known for migratory birds near Gurugram. Again, not a floating-vegetation swamp.

The concept is a Ramsar-type wetland ecosystem and the conservation issues around Loktak, including hydroelectric impact and the Loktak Development Authority. This links to Environment and to Mains GS-III questions on wetland conservation.

Trap: aspirants pick the most famous wetland bird sanctuary. Read the feature in the statement: floating vegetation points to Loktak, not a bird-centred wetland.