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': 'True about case control study \nSelect and explain. \nA. Less expensive, B. Those with disease and no diseased compared, C. Attributable risk is estimated, D. None of these', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Advantages of case-control study: Easy to carry out Rapid and inexpensive Suitable to investigate rare disease Require comparatively few subjects Risk factors can be identified No attrition problems Ethical problems minimal (pg no: 74 park 23 rd edition)', 'role': 'assistant'}]