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
[{'content': 'Smooth muscle relaxant nitric oxide is synthesized from: \nSelect and explain. \nA. Methionine, B. Cyseine, C. Arginine, D. Ornithine', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. (c) ArginineRef: Harper's Biochemistry 30th edn. 1314, 660-61", 'role': 'assistant'}]