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': 'A patient using contact lens develops corneal infection. Laboratory diagnosis of acanthomoeba keratitis was established. The following is the best drug for treatment: \nSelect and explain. \nA. Propamidine, B. Neosporine, C. Ketoconazole, D. Polyhexamethylene biguanide', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Polyhexamethylene biguanide', 'role': 'assistant'}]