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': 'All of the following are true about case control study except ? \nSelect and explain. \nA. Rapid and inexpensive, B. No risk to subjects, C. Risk factor can be identified, D. Less prone to bias', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Less prone to bias", 'role': 'assistant'}]