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 of the following is characteristic of a single exposure common vehicle outbreak ? \nSelect and explain. \nA. Frequent secondary cases, B. Severity increases with increasing age, C. Explosive, D. Cases occur continuously beyond the longest incubation period', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Explosive", 'role': 'assistant'}]