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': 'True about case control study - \nSelect and explain. \nA. Less expensive, B. Those with disease and not diseased compared, C. Attributable risk is estimated, D. None of these', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Less expensive", 'role': 'assistant'}]