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 associated with one carbon transfer is: 
Select and explain. 
A. Niacin, B. Thiamine, C. Ascorbic acid, D. Folic acid
D: Folic acid
Answer: D: Folic acid 
Explanation: None