This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
25-di hydroxy cholecalciferol is converted to 1,25-dishy- drocholecalciferol in: 
Select and explain. 
A. Skin, B. Kidney, C. Lung, D. Liver
B: Kidney
Answer: B: Kidney 
Explanation: None