The correct option is C Emphysema
Emphysema is a group of lung diseases which block the airflow and make breathing difficult. As in this condition, the inner walls of the air sac get rupture and creating one larger air space. This reduces the surface area of the lungs and thus, reduces the amount of oxygen to reach the bloodstream.
Alpha-1 antitrypsin is a protease inhibitor and it is used to treat emphysema because it protects tissues from enzymes of inflammatory cells.