I think the answer is emphysema. the definition of it is "a condition in which the air sacs of the lungs are damaged and enlarged, causing breathlessness."
the definition for asthma is "a respiratory condition marked by spasms in the bronchi of the lungs, causing difficulty in breathing. It usually results from an allergic reaction or other forms of hypersensitivity."
pneumonia is an infection where the lungs start to fill with fluid.
Cancer is usually a tumour inside the lungs.
The answer would be A