Q. The presence of Susu is an indication of the health of the river.
Which of the following is related to susu?

[A] Crocodiles

[B] Dolphins

[C] Fishes

[D] Mollusks

Answer: B
Notes:

Explanation: In the fresh waters of River Ganga and River Brahmaputra, a variety of dolphin locally called Susu (also called blind dolphin) is found. The presence of Susu is an indication of the health of the river. The untreated industrial and urban wastes with high amount of chemicals are killing this species.

Source: NCERT