This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Which vitamin required for hydroxylation of proline? 
Select and explain. 
A. A, B. D, C. C, D. K
C: C
Answer: C: C 
Explanation: Vitamin-c is required for hydroxylation of proline and lysine They form cross links and maintain stability of collagen Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:229