This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acid Metabolism, Subject name: Biochemistry
Smooth muscle relaxant nitric oxide is synthesized from: 
Select and explain. 
A. Methionine, B. Cyseine, C. Arginine, D. Ornithine
C: Arginine
Answer: C: Arginine 
Explanation: Ans. (c) ArginineRef: Harper's Biochemistry 30th edn. 1314, 660-61