What Aspect of Circadian Rhythms Might Explain Why We Tend

Multiple Choice

What aspect of circadian rhythms might explain why we tend to feel so tired at night?

A) body temperature bottoms out on Monday mornings
B) the three biorhythm patterns converge at low points on Mondays
C) heart rates typically increase at night
D) there is an organ in the brain sensitive to light changes, which then affects our sleepiness