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
"Chancroid" is caused by: 
Select and explain. 
A. H. ducreyi, B. H. influenzae, C. H. aprophilus, D. All the above
A: H. ducreyi
Answer: A: H. ducreyi 
Explanation: H. ducreyi