Which of the Following Does Not Characterize a Free-Running Circadian

Multiple Choice

Which of the following does not characterize a free-running circadian rhythm?

A) If the period is less than 24 hours, the animal begins its activity a little later each day.
B) Its period is under genetic control.
C) It occurs under constant environmental conditions.
D) Its clock runs according to its natural period.
E) Mutations can create differences in period lengths within a species.