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': 'Prevalence is a: September 2007 \nSelect and explain. \nA. Rate, B. Ratio, C. Propoion, D. Percentage', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: Propoion', 'role': 'assistant'}]