This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Prevalence is a \nSelect and explain. \nA. Rate, B. Ratio, C. Propoion, D. Mean', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ref: Parks 23rd edition pg 61 Prevalence is a propoion. Time is not mentioned. Point prevalence of a disease is defined as the number of all current cases (old and new) of a disease at one point of time, in relation to a defined population.', 'role': 'assistant'}]