This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology metabolism, Subject name: Physiology
Hormonal vitamin is- 
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 o Active form of vitamin D i.e. 1-25 dihydroxy-cholecalciferol is a vitamin produced in kidney,o It acts on intranuclear receptors to regulate gene expressions (transcription factors).