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': 'If one wants to compare in two characteristics with variable difference, which measurement should be used? \nSelect and explain. \nA. Standard deviation, B. Percentile, C. Variance, D. Co-efficient of variation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]