This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'Which of the following amino acid in a protein is involved in urea cycle and is required for synthesis of Nitric Oxide? \nSelect and explain. \nA. Arginine, B. Histidine, C. Tryptophan, D. Lysine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]