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
During the formation of hydroxyproline and hydroxylsine, the essential factors required is/are: 
Select and explain. 
A. Pyridoxal phosphate, B. Ascorbic acid, C. Thiamine pyrophosphate, D. Methylcobalamine
B: Ascorbic acid
Answer: B: Ascorbic acid 
Explanation: B i.e. Ascorbic acid