This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of Cornea, Subject name: Ophthalmology
[{'content': 'Most common cause of infectious keratitis in a contact lens user \nSelect and explain. \nA. Acanthamoeba, B. Pneumococcus, C. Pseudomonas, D. Staph', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Most common cause of infectious keratitis in a contact lens user is pseudomonas Commonest causative organism associated with keratitis - pneumococcus Hypopyon ulcer / ulcus serpens - pneumococcus acanthamoeba : attacks contact lens that are washed with water.', 'role': 'assistant'}]