This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins, Subject name: Biochemistry
Collagen synthesis requires which vitamin - 
Select and explain. 
A. Vitamin B1, B. Vitamin D, C. Vitamin C, D. Vitamin E
C: Vitamin C
Answer: C: Vitamin C 
Explanation: Ans. is 'c' i.e., Vitamin C o Hydroxylation of proline and lysine during collagen synthesis requires vitamin C (ascorbic acid), molecular oxygen (O2), (X-ketoglutarate and enzymes dioxygenases (prolyl hydroxylase, lysyl hydroxylase).