Question

Two characteristics used to define mammals include
a. mammary glands and scales.
b. mammary glands and hair or fur.
c. mammary glands and sweat glands.
d. sweat glands and a four-chamber heart.

Answer 1

b. mammary glands and hair or fur. things also to classify: feed milk to young, give birth live, and breathe in air, so they have lungs.

Answer 2

b. they fed their child with milk from mammary gland and their body are covered up with hair or fur not feather