In COPD which is true -

Ans. is 'a' i.e., FEV1 / FVC < 0.7 The lung function tests in obstructive lung disease can be summarized as -o Forced expiratory' vital capacity (FEVc) - Normal to slightly decreasedo Forced expiratory volume in 1 sec (FEV1)-Decrease out of proportion to FVCo FEV1/FEV1-Decrease can be as low as 20% - 30%o Peak expiratory flow rate-Decreasedo Total lung capacity-Increaseo Residual volume-Increaseso Functional residual capacity-Higher