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': 'Simplest and most common method of measuring variation is \nSelect and explain. \nA. Mean, B. Median, C. SD, D. Range', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]