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': 'Not an analytical study is: \nSelect and explain. \nA. Cross-sectional, B. Coho, C. Case-control, D. RCT', 'role': 'user'}, {'content': 'Answer: D \nExplanation: RCT', 'role': 'assistant'}]