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': 'Mean ± 250 in normal distribution \nSelect and explain. \nA. 68%, B. 95%, C. 99%, D. 50%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In normal distribution :\n\nMean\xa0± 150 lovers 68% values.\nMean\xa0± 250 lovers 95% values.\nMean\xa0± 350 lovers 99% values.', 'role': 'assistant'}]