This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sexually Transmitted Infections, Subject name: Dental
[{'content': 'Painful ulcers over genitalia seen in: \nSelect and explain. \nA. Primary syphilis, B. Granuloma inguinale, C. Chancroid, D. Lymphogranuloma venerum', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Chancroid or soft chancre Painful ulcer on penis caused by Haemophilus ducreyii . Irregular edges, undermined ulcers, bleeds easily. Painful , suppurative,unilateral inguinal lymphadenitis(bubo) : classical feature Kissing ulcers- Due to autoinoculation on the genitalia. Hard chancre painless genital ulcer most commonly formed during primary syphilis. forms approximately 21 days after the initial exposure to T.pallidum.', 'role': 'assistant'}]