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: Pathology
[{'content': 'Syphilis becomes seropositive in \nSelect and explain. \nA. Chancre (primary syphilis), B. Muco patches (secondary syphilis), C. Gurnma (tertiary syphilis), D. Congenital syphilis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]