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': 'Case control studies are also called: \nSelect and explain. \nA. Retrospective, B. Prospective, C. Prevalence, D. Incidence', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]