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: Microbiology
[{'content': 'The causative organism of syphilis is: \nSelect and explain. \nA. Borrelia burgdorferi, B. Chlamydia trachomatis, C. Leptospira interrogans, D. Treponema pallidum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]