A:
Bhitarkanika National Park
B:
Keibul Lamjao National Park
C:
Keoladeo Ghana National Park
D:
Sultanpur National Park
Explanation
The national park that is unique in being a swamp with floating vegetation that supports a rich biodiversity is the Keibul Lamjao National Park.
Keibul Lamjao National Park is located in the state of Manipur in northeastern India. It is the only floating national park in the world and is known for its unique phumdis (floating mass of vegetation) which serve as a habitat for the endangered Manipur brow-antlered deer, also known as the Sangai deer. The park is also home to various other species of flora and fauna, making it a significant biodiversity hotspot in the region.