Our tendency to feel wakeful and sleepy on a 24-hour basis depends mainly on

Question

a. a cycle generated by a mechanism in the brain
b. our perception of environmental stimuli such as heat and light
c. a cycle generated by hormone-producing organs such as the adrenal gland
d. wear and tear on the muscles followed by a period of repair

I chose answer A. because humans have mechanisms that prepare us for activity during the day and sleep at night. But the other choices seem to somewhat fit...Is this answer correct?

Answer 1

I agree that A is the best answer. However, we can modify the brain mechanism by external stimuli.