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
Which of the following is the drug of choice for treatment of corneal ulcers caused by filamentous fungi? 
Select and explain. 
A. Itraconazole, B. Natamycin, C. Nystatin, D. Fluconazole
B: Natamycin
Answer: B: Natamycin 
Explanation: B i.e. Natamycin