This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Homocystinuria is due to abnormal metabolism of \nSelect and explain. \nA. Methionine, B. Valine, C. Tryptophan, D. Leucine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Homocystinuria is a group of disorder of methionine metabolism.', 'role': 'assistant'}]