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: Dental
[{'content': 'The mean DMFT values for 12 year old school children is 2.5. 68% of the population has DMFT values between 2\nand 3. The standard deviation for the population is: \nSelect and explain. \nA. 0.5, B. 1, C. 2, D. 3', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]