Question

How are living mammals classified into groups? A. type of circulatory system B. method of development C. method of respiration D. method of regulating body temperature

Answer 1

Living animals are classified in groups by their method of development. 

Hope this helped!
Have a nice day!

Answer 2

The correct answer is option B

The mammals are further classified into groups in terms of development of the offspring. There are various types of mammals that development in different way.

Placental Mammals:

The embryo grows inside the body of the mother by the help of placenta which aids in the nourishment of the embryo. After birth, the mother cares for the young ones.

Marsupials:

They lack placenta and in place of placenta they have marsupium that provides nourishment to the young ones after birth. This is a pouch found in the body of the mother which acts as the protective covering of the embryo in which further development of the young ones takes place.

Monotremes:

These kind of mammals lay eggs, eggs are hatched and the young ones lick the milk from the abdomen of the mother.