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': "Obermeyer test comes out to be positive in which disease \nSelect and explain. \nA. Hartnup's disease, B. Phenylketonuria, C. Alkaptonuria, D. Pellagra", 'role': 'user'}, {'content': "Answer: A \nExplanation: Amino acid Trytophan gives obermeyer test positive.\nHartnup's disease is characterised by impaired absorption of neutral amino acids especially tryptophan.\nThus Tryptophan gets excreted in large amounts and gives positive obermeyer test.", 'role': 'assistant'}]