What is a defining feature of mammals that is not present in most other vertebrates? a. mammals reproduce through internal fertilization. b. mammals maintain a constant body temperature. c. mammals can produce milk for their offspring. d. mammals have a nervous system with a spinal cord.

The correct answer is C. Mammals can produce milk for their offspring.

Mammals are the members of class mammalia. The word mammalia was derived from Latin word "mamma" which means "breasts" as they had a unique feature i.e. presence of mammary glands.

These glands were evolved from a special types of sweat glands and became specialized in the production of milk, especially in females.

They help the mothers in providing nourishment to the offspring.

Other features of mammals may include four chambered heart, hair and fur, three middle ear bones, etc.

I just took a test with this question and the answer is:

69 is the correct math for the amino acids