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 following are advantages of case control study except-a) Cheaperb) Less time consumingc) Possible to study many diseasesd) Less chances of bias \nSelect and explain. \nA. bd, B. cd, C. ab, D. bd', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]