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': 'Xerophthalmia can be caused by: March 2010 \nSelect and explain. \nA. Steven-Johnson syndrome, B. Vitamin A deficiency, C. Sulfa drugs, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D: All of the above', 'role': 'assistant'}]