Question

All mammals
(a)Possess the uterus.
(b) Give birth to live young.
(c) Nourish their young ones with milk.
(d) Contain a thick coat over their young.

Answer 1

Hint: This is related to the nourishment of babies or young ones of mammals. The protein casein is present as the main nutritive constituents in it.

Complete answer:
All mammals nourish their young ones with milk. The presence of milk or mammary gland in females is one of the main characteristic features of the class Mammalia. This mammary gland helps the mother in nourishing their young ones with milk.

Additional Information:
-Milk is produced in the mammary gland and is a type of exocrine gland. The mammary glands are modified and enlarged sweat glands which gave the class its name.
-The ovarian hormone, estrogen is responsible for the development of mammary glands.
-Besides the presence of milk or mammary gland mammals are also distinguished by several other unique features such as the presence of hair all over the animal body except in some whales. The young ones neither have fur nor the thick coat over their body.
-The uterus is not present in all mammals because some mammals are viviparous and they lay eggs for example platypus and echidna are egg-laying mammals and they do not give birth to young ones, so the uterus is absent in their body. Some examples of uterus bearing mammals are dogs, dolphins, whales, elephants, and all primates.
-The presence of hair and three middle ear bones are also the characteristic features of class Mammalia; these features distinguish them from reptiles and birds.
-Almost 6,400 species of mammals have been described by biologists.

So the correct answer is, 'Nourish their young ones with milk'.

Note:
-The mammary glands that produce milk are modified and enlarged sweat glands which gave the class its name.
-Exocrine glands are glands with ducts. Secretions are released into an epithelial surface through these ducts.
-The uterus is not present in all mammals because some mammals are viviparous and they lay eggs for example platypus and echidna are egg-laying mammals and they do not give birth to young ones.