What ends the negative feedback loop? The return to normal body temperature. Sleep. Death. None of these.

Option A, The return to normal body temperature

Explanation:

In a negative feedback loop, activities or reactions are slowed down in order to maintain homeostasis. Any such action which lessens the impact of stimuli is called as negative feedback. Whenever the body temperature rises, homeostasis is achieved through temperature reduction. Similarly if the blood sugar rise, insulin is lowers the blood glucose to maintain blood sugar level. Negative feedback is neither positive nor negative it is called negative as it tends to lower the reactions or activities.  

Hence, option A is correct

answer; hydrologic cycle;