Mammals have all of the following characteristics except:​

A) ​They have body hair.
B) ​They nurse their young.
C) ​They do not give birth to live young.
D) ​They include the primates.

Mammals are defined by several key characteristics, including the presence of body hair, the ability to nurse their young with milk, and the giving birth to live young. Primates are a group of animals that are classified as mammals. Therefore, the characteristic that mammals do not have is the ability to lay eggs or give birth to young that hatch from eggs.