During sleep, mammals

A) increase muscle activity.
B) lower their body temperatures.
C) expend lots of energy.
D) are safe from danger.

Body Temperatures

The degree or intensity of heat present in a living body, typically maintained within a range that enables normal functioning.

Muscle Activity

The physiological processes of muscle contraction and relaxation, which enable movement and stabilization of the body.

Mammals

Warm-blooded vertebrate animals distinguished by the possession of hair or fur, the birth of live young, and the females' ability to produce milk for their offspring.