The correct answer is Sangai deer.
The Keibul Lamjao National Park is a national park in Manipur, India. It is the only floating national park in the world, and is known for the endangered Sangai deer. The park is located on the Loktak Lake, which is the largest freshwater lake in northeastern India. The Sangai deer is a type of deer that is found only in Manipur. It is a small deer with long, spiral horns. The Sangai deer is an endangered species, and the Keibul Lamjao National Park is one of the few places where it can be found.
The other options are incorrect because they are not endangered species that are found in the Keibul Lamjao National Park. The Hoolock gibbon is a type of ape that is found in Southeast Asia. The clouded leopard is a type of cat that is found in Southeast Asia and China. The one-horned rhinoceros is a type of rhinoceros that is found in India and Nepal.