This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
Active form of vitamin D is: 
Select and explain. 
A. Calcitriol, B. Calcifediol, C. Cholecalciferol, D. Ergocalciferol
A: Calcitriol
Answer: A: Calcitriol 
Explanation: 1,25-dihydroxycholecalciferol or calcitriol is the active form of Vit-D .