Cholecalciferol, Formed by the Action of Sunlight on 7-Dehydrocholesterol in the Skin

Multiple Choice

Cholecalciferol, formed by the action of sunlight on 7-dehydrocholesterol in the skin, has to be converted to the fully active calcitriol before it can induce its physiological actions.The rate-limiting step in this process is catalyzed by an enzyme in:

A) The lungs.
B) The liver.
C) The brain.
D) The kidneys.
E) The intestines.