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
Filamentary keratitis may occur: 
Select and explain. 
A. In trachoma, B. In kerato conjunctivitis sicca, C. Following cataract surgery, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. All of the above