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
A 30-year-old man with history of multiple exposures presents with painful non indurated ulcer on the glans penis since 5 days. The undermined sloughed edges of margins were noted. The most probable diagnosis is? 
Select and explain. 
A. Treponema pallidum, B. Haemophilus ducreyi, C. Herpes, D. Chlamydia
B: Haemophilus ducreyi
Answer: B: Haemophilus ducreyi 
Explanation: Multiple, painful, punched-out ulcers with undermined borders is typical of chancroid. Haemophilus ducreyi is the causative agent of chancroid. It is a highly contagious but curable disease. Painless,indurated ulcer is seen in primary chancre caused by T. pallidum