Trahn works the night shift in the city hospital. During the middle of the shift he often becomes very tired. This is when his body temperature is at its lowest, and his biological clock is telling him it is time to sleep. Trahn is affected by what psychologists call __________

A) subjective night.
B) objective night.
C) disruptive malaise.
D) melatonin flux.

Biological Clock

An internal timing mechanism in organisms that controls the cycle of daily activities, such as sleep and wakefulness, based on a roughly 24-hour period.

Subjective Night

The time during a 24-hour period when the biological clock is telling a person to go to sleep.

Melatonin Flux

Variations in the levels of melatonin, a hormone that regulates sleep-wake cycles, typically influenced by light exposure.