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
CH2 transfer reaction is mediated by: 
Select and explain. 
A. Folic acid, B. Butyric acid, C. Vit. 1312, D. None of the above
A: Folic acid
Answer: A: Folic acid 
Explanation: Folic acid