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: Skin
[{'content': 'Incubation period of syphilis is: September 2006 \nSelect and explain. \nA. 10-14 days, B. 30-60 days, C. 9-90 days, D. 3-6 months', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: 9-90 days Acquired syphilis: - Primary syphilis: incubation period 2-3 weeks (range 9-90 days): local infection - Secondary syphilis: incubation period 6-12 weeks (range 1-6 months): generalised infection - Early latent syphilis: asymptomatic syphilis of less than 2 years duration - Late latent syphilis: asymptomatic syphilis of 2 years or longer duration - Late symptomatic syphilis (teiary syphilis): cardiovascular syphilis, neurosyphilis, gummatous syphilis Congenital syphilis: - Early congenital syphilis occurs within the first 2 years of life. - Late congenital syphilis emerges in children older than 2 years.', 'role': 'assistant'}]