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': 'Following are true about coho study, except: \nSelect and explain. \nA. Large number of subjects, B. Expensive, C. Suitable for common diseases, D. Less time consuming', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Less time consuming', 'role': 'assistant'}]