Explanation:

Explanation

Obligate freshwater dolphin

Yangtze river dolphin (Baiji)

• Listed as critically endangered in IUCN redlist and now likely extinct from the Yangtze river in China. It is a type of freshwater dolphin thought to be the first dolphin species driven to extinction due to the impact of humans.

Indus river dolphin (Bhulan)

• Listed as endangered in IUCN redlist.Now it swims in the lower parts of the Indus River in Pakistan. Another small, isolated population can be found in the Beas River in India.

Amazon river dolphin (Boto or pink river dolphin)

• Listed as vulnerable in IUCN redlist.It swims throughout much of the famed South American river basin and the neighboring Orinoco river basin that stretches through Colombia and Venezuela.

Ganges river dolphin (Susu)

• Listed as endangered in IUCN redlist.
• Locally known as susu, which refers to the noise the dolphin is said to make when it breathes, this swimmer is essentially blind and can detect only the direction of light.