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
Least useful anti-rachitic: 
Select and explain. 
A. 1, 25-hydroxy cholecalciferol (calcitriol), B. Cholecalciferol, C. 25-hydroxy cholecalciferol, D. Calcium
B: Cholecalciferol
Answer: B: Cholecalciferol 
Explanation: Ans: B, or D (Cholecalciferol or. Calcium) Ref: Nelson's Textbook of Pediatrics. 19th Edition and CRC Desk Reference for Nutrition, Second Edition, By Carolyn D. BerdanierExplanation:Sorry, I am not sure of the answer since I could not find the source or references for this question. "Nutrients that are required for normal bone growth and developement. Vitamin C. Vitamin D and minerals (Calcium, phosphorous, magnesium, manganese, pottassium . These nutrients are called Antirachitic because they prevent the development of rickets.") Ref: CRC DeskVitamin D Production