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': 'Point source epidemic tends to -a) Continue over one incubation periodb) Produce multiple peaks in the epidemic curvec) Be explosived) Tail gradually \nSelect and explain. \nA. bd, B. ac, C. bcd, D. da', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]