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': 'Which is false about coho study - \nSelect and explain. \nA. Incidence can be measured, B. Used to study chronic diseases, C. Expensive, D. Always prospective', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Always prospective", 'role': 'assistant'}]