Question

which is not a hand of the circadian clock?
a. sleep
b. locomotor activity
c. gene expression
d. hormone secretion

Explanation:

The circadian clock regulates sleep - wake cycles, locomotor activity, and hormone secretion. Gene expression is a fundamental cellular process and not specifically considered a "hand" of the circadian clock in the same way as the others which are more directly observable rhythmic behaviors or physiological processes regulated by the circadian clock.

Answer:

C. Gene expression