This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mental Health, Subject name: Social & Preventive Medicine
[{'content': 'IQ in profound mental retardation - \nSelect and explain. \nA. 50 - 70, B. 35 - 50, C. 20 - 35, D. < 20', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., < 20 The Intelligence Quotient (I.Q.) is calculated according to the formula:IQ =Mental age----------------Chronological agex 100The WHO classification of mental retardation is based on the concept of IQ and includes the following categories:CategoryIQMild50-70Moderate35-49Severe20-34Profound<20A child with IQ < 70 is called mentally retarded.", 'role': 'assistant'}]