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: Forensic Medicine
[{'content': 'Mental retardation is defined when I.Q. is below : \nSelect and explain. \nA. 90, B. 80, C. 70, D. 65', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. 70', 'role': 'assistant'}]