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
Which of the following is required for the conversion of 25-hydroxy-cholecalciferol to calcitriol? 
Select and explain. 
A. 25-hydroxylase, B. 1-hydroxylase, C. UV light, D. 1,25-hydroxylase
B: 1-hydroxylase
Answer: B: 1-hydroxylase 
Explanation: None