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
Which vitamin is required for transfer of 1-carbon unit ? 
Select and explain. 
A. Vitamin A, B. Folic acid, C. Vitamin B12, D. Niacin
B: Folic acid
Answer: B: Folic acid 
Explanation: Ans. is 'b' i.e., Folic acid