This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Antibiotics, Subject name: Pharmacology
[{'content': 'The drug of choice for secondary syphilis? \nSelect and explain. \nA. Chloramphenicol, B. Benzathine penicillin, C. Doxycycline, D. Vancomycin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Penicillins are the drug of choice for syphilis.Ref: KDT 5th ed Pg:657', 'role': 'assistant'}]