This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
True about chronic obstructive pulmonary disease (COPD) 
Select and explain. 
A. FEVI <30 of predicted value, B. FEV1/FVC<0.7, C. total lung capacity increased, D. All
D: All
Answer: D: All 
Explanation: In COPD,airflow obstruction is demonstrated by spirometry in which the post- bronchodilator FEV1/FVC is less than 70%.The severity of COPD may be defined in relation to the post - bronchodilator FEV1 which is <30% predicted in very severe type.Measurement of lung volumes provides an assessment of hyperinflation.COPD is characterised by increase in residual volume,residual volume/total lung capacity ratio,and progressive hyperinflation(increased total lung capacity) late in the disease. source : Harrison 20 th edition.