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': 'Cross sectional study is implicated in: \nSelect and explain. \nA. Study of chronic disease., B. Study of rare disease., C. Study of sudden outbreak., D. All of the above.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cross-sectional:\nGives PREVALENCE.\nStudies one point at a time (One point study). Different individual of SAME age group ,studied only once - 1 point study\nIs very important in Study of SUDDEN OUTBREAK OF DISEASE.', 'role': 'assistant'}]