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. H. influenzae, C. H. aprophilus, D. All the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: H. ducreyi', 'role': 'assistant'}]