This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acids Basics, Subject name: Biochemistry
Vitamin synthesized from amino acid is? 
Select and explain. 
A. Thiamine, B. Riboflavin, C. Biotin, D. Niacin
D: Niacin
Answer: D: Niacin 
Explanation: Ans. (d) NiacinRef Harper's Biochemistry 28/e, chapter 44