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: Psychiatry
[{'content': 'Mild mental retardation is characterized by \nSelect and explain. \nA. IQ : 90 - 109, B. IQ : 70 - 89, C. IQ : 50 - 69, D. IQ : 35 - 49', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Normal : 90 - 109.\nBorerline : 70 - 89.\nMild : 50 - 69.\nModerate : 35 - 49.\nSevere : 20 - 34.', 'role': 'assistant'}]