This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'Incubation period of syphilis: \nSelect and explain. \nA. 1 hour - 5 hours, B. 24 hours - 48 hours, C. 1 day-10 days, D. 10 days - 90 days', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., 10 days-90 daysRef: Ananthanarayan, 9th/e,p 370 and 372; Harrison, 18th/e, p. 381, 382 and 19th/e, p. 1132)IP - 9-90 days", 'role': 'assistant'}]