Classification Of Animals

Whales, Bat, Kangaroo and Hippopotamus are the one that belongs to the class mammalia. Some of the specific characteristics of the class are as follows: presence of hair or fur, they have specific mammary glands that produce milk in order to nourish the offspring. They are warm blooded and have diaphragm.
Penguin, ostrich are not mammals.

So, the correct answer is (D): whale, bat, kangaroo, hippopotamus