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': 'Young male with painless induration of penis, enlarged non tender genital lymph nodes. Cause is - \nSelect and explain. \nA. Chancroid, B. Herpes genitalis, C. Primary syphilis, D. Donovanosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]