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: Surgery
[{'content': 'Painless ulcer of the tongue is due to : \nSelect and explain. \nA. Dyspepsia, B. Syphilis, C. Tuberculosis, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Syphilis chancres can occur in the mouth and they are painless.', 'role': 'assistant'}]