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: Biochemistry
Active form of vitamin D in kidney is: 
Select and explain. 
A. 1 dihydroxy cholecalciferol, B. 25 hydroxy cholecalciferol, C. 1, 25 dihydroxy cholecalciferol, D. 7 dihydroxy calciferol
C: 1, 25 dihydroxy cholecalciferol
Answer: C: 1, 25 dihydroxy cholecalciferol 
Explanation: None