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': 'Regarding point source epidemic true -a) Rapid rise and fallb) Only infectious causec) Explosived) ↑ secondary attack ratee) No secondary wave \nSelect and explain. \nA. ae, B. edb, C. ace, D. bd', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]