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
Xerophthalmia can be caused by: March 2010 
Select and explain. 
A. Steven-Johnson syndrome, B. Vitamin A deficiency, C. Sulfa drugs, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. D: All of the above