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: Social & Preventive Medicine
[{'content': 'A person with IQ of 55 is \nSelect and explain. \nA. Mild mental Retandation, B. Moderate Mental Retandation, C. Severe Mental Retandation, D. Very Severe Mental Retandation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]