This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology and Reproduction, Subject name: Physiology
Which vitamin acts as a hormone- 
Select and explain. 
A. Niacin, B. Pyridoxin, C. Vitamin D, D. Riboflavin
C: Vitamin D
Answer: C: Vitamin D 
Explanation: Ans. is 'c' i.e., Vitamin D * Vitamin D and retinoic acid (Vitamin A) acts on endocrine intranuclear receptors and therefore are considered as hormonal Vitamin D.