This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'Nitric acid in synthesized from \nSelect and explain. \nA. L-arginine, B. L-citrulline, C. Lysine, D. Trptophan', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref-Sathyanarayana 4/e p387 Dietary supplements containing L-arginine have been marketed with the purpose of increasing vasodilatation, and thus, blood and oxygen supply to the exercising muscle. The present study evaluated the acute effect of L-arginine supplementation on indicators of NO production, nitrite (NO2-) + nitrate (NO3-) (NOx), in healthy subjects.', 'role': 'assistant'}]