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': 'Evidence based medicine, which of the following is not useful -a)  Personal exposureb)  RCTc)  Case reportd)  Meta-analysise) Systemic review \nSelect and explain. \nA. a, B. ac, C. ad, D. b', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]