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
Pellagra is caused by the deficiency of 
Select and explain. 
A. Niacin, B. folic acid, C. glycin, D. ascorbic acid
A: Niacin
Answer: A: Niacin 
Explanation: None