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
Which of the following statement regarding COPD is true? 
Select and explain. 
A. Decrease FEV1, B. Increased RV, C. Diffusion capacity is decreased, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Spirometry findings in COPD includes reduced FEV1 and a reduced FEV1 / FVC ratio. Diffusion capacity for carbon monoxide reflects the ability of lung to transfer gas across alveolar/capillary interface. Diffusion capacity is low in patients with emphysema and infiltrative lung diseases. It is increased in patients with pulmonary hemorrhage, congestive hea failure and asthma. Reference: Current Medical Diagnosis and Treatment 2013, chapter 9.