Question

practice it
pattern of fluctuations in bodily processes that occur regularly each day
endocrine system
auditory system
circadian rhythm
gene expression
body temperature

Explanation:

The endocrine system is about hormone - secreting glands. The auditory system is related to hearing. Gene expression is about how genes are used to make proteins. Body temperature is a single physiological variable. Circadian rhythm specifically refers to the 24 - hour pattern of fluctuations in bodily processes.

Answer:

circadian rhythm