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': 'Best method of variability is - \nSelect and explain. \nA. Mean, B. Mode, C. Median, D. Standard deviation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: "Standard deviation is most common and generally most appropriate measure of dispersion (variation)". — Park', 'role': 'assistant'}]