This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
A 67-year-old woman has pulmonary function tests performed to evaluate symptoms of dyspnea. The most prominent finding is a reduction of the ratio of FEV1/FVC. Which of the following is the most likely diagnosis? 
Select and explain. 
A. COPD, B. ankylosing spondylitis, C. Pickwickian syndrome, D. scleroderma of the chest wall
A: COPD
Answer: A: COPD 
Explanation: The VC is reduced in emphysema, but the FEV1 is grossly reduced because of high airway resistance. In predominant emphysema, diffusing capacity is more profoundly decreased than in predominant bronchitis.