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
[{'content': 'Hypopyon corneal ulcer is caused by \nSelect and explain. \nA. Pneumococcus, B. Pseudomonas, C. Herpes simplex, D. Neisseria gonorrhoeae', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Since pneumococcus invariably causes hypopyoin, its called Hypopyon Corneal ulcer.', 'role': 'assistant'}]