Question

the biological clock that operates in human beings to adjust their functioning to night-and-day periodicity is referred to as
a spontaneous neural activity
b a fixed-interval schedule
c a circadian rhythm
d active consciousness

Explanation:

The biological clock in humans that adjusts functioning to night - day cycles is known as a circadian rhythm. Spontaneous neural activity (A) is not related to this cycle adjustment. A fixed - interval schedule (B) is a concept in operant conditioning, not about biological clocks. Active consciousness (D) also doesn't refer to the biological clock for day - night adjustment.

Answer:

C. a circadian rhythm