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: Ophthalmology
Hypopyon corneal ulcer is caused by 
Select and explain. 
A. Pneumococcus, B. Pseudomonas, C. Herpes simplex, D. Neisseria gonorrhoeae
A: Pneumococcus
Answer: A: Pneumococcus 
Explanation: Since pneumococcus invariably causes hypopyoin, its called Hypopyon Corneal ulcer.