Question

33 minutes remaining5 of 50 questions remainingtest contentpage 45 of 50question 452 pointsmost people are awake during the day and asleep at night because their ______ cycles are aligned with the outside world.diurnalcircadianselectedmelatoninexternalclear selection

Explanation:

Circadian cycles are the 24-hour internal biological rhythms that regulate sleep-wake patterns, aligning with day-night cycles. "Diurnal" refers to being active during the day, not the cycle itself. Melatonin is a hormone that aids sleep, not the cycle. "External" does not describe the internal biological cycle in question.

Answer:

B. circadian