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: ENT
[{'content': 'Most comon cause of obstruction in atrophic rhinitis is \nSelect and explain. \nA. Excessive formation of crust, B. Polyp, C. Synechiae, D. Hypertrophy of turbinate', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]