This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Social science, Mental health & Genetics, Subject name: Social & Preventive Medicine
[{'content': 'Most common type of mental retardation - \nSelect and explain. \nA. Mild, B. Moderate, C. Severe, D. Profound', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The number of mild cases far exceed the severe and profound cases English statistics suggest that among 100 mentally handicaped persons 70 mild, 20 moderate, 5 severe cases WHO classification of Mental retardation(MR) mild MR...IQ 50-70 moderate MR ...35-49 severe MR..IQ 20-34 profound MR...IQ under 20 ref; (page no;582) 23rd edition of PARK&;s textbook of Preventive and Social medicine', 'role': 'assistant'}]