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 true about propagated epidemics ? \nSelect and explain. \nA. Gradual rise, B. Gradual fall, C. Person to person transmission, D. No secondary wave', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., No secondary wave", 'role': 'assistant'}]