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: Pediatrics
[{'content': 'Which of the following is a preventable cause of mental retardation – \nSelect and explain. \nA. Hypothyroidism, B. Down syndrome, C. Cerebral palsy, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]