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': '. A case control study is not characterized by - \nSelect and explain. \nA. Cases with the disease are compared to controls without the disease -, B. Assessment of past exposure may be blased, C. Definition of cases may be difficult, D. Incidence rates may be computed directly', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]