This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Renal Regulation of Minerals, Subject name: Physiology
25-di hydroxy cholecalciferol is converted to 1,25-dihy- drocholecalciferol in: 
Select and explain. 
A. Skin, B. Lung, C. Liver, D. Kidney
D: Kidney
Answer: D: Kidney 
Explanation: Ans. (d) KidneyRef: Ganong 23rd ed. / 674