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': 'What is the most likely diagnosis if a urine sample collected for routine testing darkens on standing? \nSelect and explain. \nA. Phenylketonuria, B. Alkaptonuria, C. Maple syrup disease, D. Tyrosinemia', 'role': 'user'}, {'content': "Answer: B \nExplanation: Urine turns dark on standing in alkaptonuria due to the formation of black coloured alkaptone bodies. Ref: Textbook of Biochemistry By DM Vasudevan, 3rd Edition, Page 184 ; Harper's Biochemistry, 25th Edition, Page 332", 'role': 'assistant'}]