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': 'A 16 year old male is found to have a mental age of 9 years on I.Q. testing. He has - \nSelect and explain. \nA. Mild mental retardation, B. Moderate mental retardation, C. Severe mental retardation, D. Profound mental retardation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]