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
Vitamin required for hydroxyproline to proline conversion: 
Select and explain. 
A. Vitamin C, B. Vitamin E, C. Pvrodoxal PO4, D. Biotin
A: Vitamin C
Answer: A: Vitamin C 
Explanation: A i.e. Vitamin C