Activity levels of the green iguana vary in cycles that are repeated every 24 hours.  It is logical to assume that alteration in the intensity of incident light is the stimulus that controls these daily biological rhythms.  But there is much evidence to contradict this hypothesis.

Which of the following, if known, is evidence that contradicts the hypothesis stated above?

A.  The temperature of the green iguana varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning.

B.  While some animals, such as the rabbit, are much more active during the day, others, such as moles, show greater activity at night.

C.  When animals are transported from one time zone to another, their daily biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.

D.  Other types of iguanas display similar activity cycles even though they live in very different climates.

E.  Even when exposed to constant light intensity around the clock, some iguanas display rates of activity that are much greater during daylight hours than at night.  
 
The best answer is E.  If iguanas that are exposed to light 24 hours a day display a similar pattern of activity as those exposed to natural light and dark cycles this constitutes evidence again the hypothesis that it is the alterations in light that control biological cycles.