This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amino Acid Metabolic Disorder, Subject name: Biochemistry
[{'content': 'Cystinuria presents with excess of \nSelect and explain. \nA. Cysteine, B. Tyrosine, C. Glutamine, D. Valine', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) CysteineRef: Harper's Biochemistry 30th edn. 1301", 'role': 'assistant'}]