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': 'Parenchymatous xerosis of conjunctivitis is caused by \nSelect and explain. \nA. Trachoma, B. Vitamin A deficiency, C. Vernal catarrh, D. Phlyctenular keratoconjunctivitis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Trachoma Vit A deficiency causes epithelial xerosisQ. Parenchymal xerosis is caused by widespread destructive interstitial conjunctivitis as seen in trachoma Q, diptheria, Steven Jonson Syndrome, pemphigus or pemphigoid conjunctivitis, thermal, chemical or radiational burns of conjunctiva Q and exposure of conjunctiva.', 'role': 'assistant'}]