This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'In which of the following forms of pulmonary carcinoma is the classic progression of metaplasia to dysplasia to carcinoma in situ observed \nSelect and explain. \nA. Small-cell carcinoma, B. Adenocarcinoma, C. Large-cell carcinoma, D. Squamous cell carcinoma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: All stages from squamous metaplasia to carcinoma in situ are observed in squamous cell carcinoma. Such a clear progression is not seen in the other forms of cancer listed.', 'role': 'assistant'}]