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': 'Chancroid is caused by - \nSelect and explain. \nA. H. ducreyi, B. T. pallidum, C. Gonococcus, D. HSV', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]