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': 'Ligneous conjunctivitis is caused by: \nSelect and explain. \nA. Purulent conjunctivitis, B. Membranous conjunctivitis, C. Angular conjunctivitis, D. Phlyctenular conjunctivitis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Membranous conjunctivitis', 'role': 'assistant'}]