The endogenous nature of biological rhythms is based on the ...

[Millan]

The endogenous nature of biological rhythms is based on the observations that animals isolated from light and dark cues
A) continue to have cycles of exactly 24 hours' duration.
B) continue to have cycles of approximately 24 hours' duration; some more rapid, some slower.
C) synchronize activity with whatever lighting cycle is imposed on them.
D) cease having any rhythms.
E) are independent of any genetic determinants.

[Celeste]

B