This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Anatomy
A child Mahesh has been diagnosed to be having vitamin D dependent rickets. The most appropriate vitamin D preparation for him is: 
Select and explain. 
A. Calciferol, B. Cholecalciferol, C. Calcifediol, D. Calcitriol
D: Calcitriol
Answer: D: Calcitriol 
Explanation: (Ref: KDT 6/e p390) Most active vitamin D preparation is calcitriol.