This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Physiology
Most active form of vitamin D 
Select and explain. 
A. Calcefedial, B. Calcitriol, C. 7-dehydrocholecalciferal, D. Vitamin D3
B: Calcitriol
Answer: B: Calcitriol 
Explanation: Vitamin D- is a fat-soluble vitamin, chemically related to the steroids and essential for the normal formation of bones and teeth and for the absorption of calcium and phosphorus from the GI tract.1a,25-Dihydroxycholecalciferol (or 1,3,25-triol); or calcitriol is the active form of vitamin D, it is more potent than calcidiol. Ref: Ganong&;s review of medical physiology;24th edition; page no-379