This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'A 6-year-old child is brought to the OPD with a history of mental retardation, failure to walk , failure to grow, seizures, hyperactivity, and tremors. On examination, there is microcephaly, fair hair, light skin color, and blue eyes. Which of the following enzyme is deficient in this child? \nSelect and explain. \nA. Homogentisate dioxygenase, B. Tyrosinase, C. Fumaryl acetoacetate hydroxylase, D. Phenylalanine hydroxylase', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The given clinical manifestations point to the diagnosis of Phenylketonuria (PKU). Deficiency of the enzyme phenylalanine hydroxylase Reference: Harpers illustrated biochemistry 30th edition', 'role': 'assistant'}]