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: Skin
Chancroid is caused by? 
Select and explain. 
A. H. Ducrei, B. N. Gonnorrea, C. T. Pallidum, D. H. Influenza
A: H. Ducrei
Answer: A: H. Ducrei 
Explanation: Ans:A.)H. Ducrei CHANCROID (SOFT SORE) This venereal infection is caused by the Gram-negative bacillus Haemophilus ducreyi. One to 5 days post-infection, a soft sloughy ulcer appears on the penis or vulva. The treatment of choice is erythromycin (500 mg 6-hourly for 14 days).