Double vagina are found in

Mammals that give birth to relatively undeveloped young and raise them in a pouch are called ....

In echolocation,the animal that produces high frequency sounds is

Which one of the following characteristics is not shared by birds and mammals?

Common among all mammals is

Assertion : The duck-billed Platypus and the spiny ant-eater,both are egg-laying animals yet they are grouped under mammals.
Reason : Both of them have seven cervical vertebrae and $12$ pairs of cranial nerves.