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 related to a co-factor in glycine Metabolism? 
Select and explain. 
A. V, E, B. Folic acid, C. Thiamine, D. Pantothenic acid
B: Folic acid
Answer: B: Folic acid 
Explanation: Tetrahydrofolic acid and S- adenosyl methionine act as a carrier compound for single carbon units.