The pea-sized gland that is stimulated by light and helps regulate activity levels over the course of a day is the:

A) adrenal
B) pituitary
C) pineal
D) thyroid

Pineal Gland

The pineal gland, a tiny gland located in the brain, secretes the hormone melatonin, which plays a crucial role in controlling the patterns of sleep and wakefulness.

Activity Levels

Refers to the degree of physical exertion or mental engagement in tasks or actions by an individual or group.