Vitamin D3 Formed Within the Skin Has All of These

Multiple Choice

Vitamin D3 formed within the skin has all of these effects on other organ systems, except that it

A) is essential for bone maintenance and growth of the skeletal system.
B) functions as a precursor for the hormone calcitriol in the endocrine system.
C) is essential for muscle contractions of the muscular system.
D) functions in the activation of innominate cells by the lymphoid system.
E) is essential for absorption of calcium and phosphorus by the digestive system.