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: Dental
[{'content': 'Incubation period of syphilis is: \nSelect and explain. \nA. 9-90days, B. 10-14days, C. 10-21days, D. 15-30days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]