In which of the following groups does the aortic arch curve to the left?

Whales are warm-blooded animals that live in cold seas. Which part of their body helps them maintain their body temperature?

Eutherian mammals are

Point out the mammalian characters.

Complete the following analogy with respect to the habitat of mammals.
Fossorial mammals: $i$ :: Arboreal mammals: $ii$

Egg-laying mammals are grouped as