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: Medicine
[{'content': 'A primary syphilitic lesion of the male genitalia characterized by: \nSelect and explain. \nA. soft, ragged ulcer, B. punched out painless ulcer with indurated edges, C. raised, flat, greyish, moist confluent lesions, D. necrotic rubbery lesion', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]