Mammals are warm-bloodedanimals with four-chamberedhearts. They have mammary glands for the production of milk tonourish their young.Their skin has hairs aswell as sweat and oil glands. Most mammals familiar to us produce live young ones. However, a few of them, like the platypus and the echidna lay eggs, and some, like kangaroos give birth to very poorlydeveloped young ones.
Answer Referred from NCERT book