The Breaking Open of Alveoli in People Who Have Emphysema

The breaking open of alveoli in people who have emphysema decreases their rate of gas exchange because

A) there is a decrease in the distance between the air they breathe in and their blood.
B) there is less pressure in the lungs to force the oxygen to dissolve in their blood.
C) the concentration of oxygen in their lungs becomes much greater than the concentration of oxygen in their blood.
D) their lungs have less surface area available for diffusion.