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': 'All are known to cause conjunctival xerosis except: \nSelect and explain. \nA. Trachoma, B. Membranous conjunctivitis, C. Angular conjunctivitis, D. Ocular pemphigoid', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Angular conjunctivitis', 'role': 'assistant'}]