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: Medicine
[{'content': 'All pulmonary function abnormalities are seen in COPD it , Except - \nSelect and explain. \nA. Decreased FEV1, B. Decreased maximum expiratory flow rate, C. Increased residual volume, D. Decreased diffusing capacity', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]