Human sleep patterns are sensitive to environmental cues such as lightness and darkness as supported by all of these statements with the exception of:
a. Circadian rhythm responds to light-producing stimuli in day-to-day life.
b. People in rural areas tend to have circadian rhythms that match natural sunrise-sunset patterns.
c. Treatment of circadian rhythm disorders often includes bright light therapy.
d. People in urban areas tend to have circadian rhythms that match natural sunrise-sunset patterns.