This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition & Digestion, Subject name: Biochemistry
In one carbon metabolism when Serine converted to Glycine, which carbon atom is added to THFA? 
Select and explain. 
A. Alpha carbon, B. Beta carbon, C. Delta carbon, D. Gamma carbon
B: Beta carbon
Answer: B: Beta carbon 
Explanation: Ans. B. Beta carbon