This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and PNS, Subject name: ENT
[{'content': 'Chronic dacrocystitis is due to? \nSelect and explain. \nA. Obstruction in naso lacrimal duct, B. Narrow bony canal, C. Foreign body, D. All of above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: ANSWER: (D) All of aboveREF: Khurana 4th ed p. 370Etiology of chronic dacryocystitis is due to obstruction and stasis AETIOLOGY:Nasolacrimal obstructionNarrow" bony canalExcessive folds in nasolacrimal ductForeign bodyExcessive lacrimationMild grade inflammation', 'role': 'assistant'}]