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: Pathology
[{'content': 'The most common site and type of metaplasia are : \nSelect and explain. \nA. Respiratory tract epithelium, Columnar metaplasia, B. Respiratory tract epithelium, Squeamous metaplasia, C. Esophagus, Squeamous metaplasia, D. Esophagus, Columnar metaplasia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: As respiratory tract is exposed to chronic irritation due to dust, Smoke etc, it undergoes squeamous\xa0metaplasia ,', 'role': 'assistant'}]