This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamin D, Subject name: Pediatrics
Most potent form of vitamin D is - 
Select and explain. 
A. Ergocalciferol (Vit. D2), B. 7 dehydro cholecalciferol, C. 25 hydroxy cholecalciferol, D. 1,25 dihydroxy cholecalciferol
D: 1,25 dihydroxy cholecalciferol
Answer: D: 1,25 dihydroxy cholecalciferol 
Explanation: Ans. is 'd' i.e., 1,25 dihydroxy cholecalciferol o 1,25 cholecalciferol also k/a calcitriol is active form of Vit. D.o Cholecalciferol in liver continued to 25 hydroxy cholecalciferol.o in kidney 25-Hydroxvcholecalciferol converted into 1,25-Hydroxy cholecalciferol.