Final answer:
Atelectasis is the disease that involves incomplete expansion of the lung, differentiating it from pneumonia, tuberculosis, epistaxis, and asthma, which involve other issues with the lungs or airways. Option a.
Step-by-step explanation:
From the diseases listed, atelectasis option a, involves the incomplete expansion of the lung. In atelectasis, the alveoli within the lungs are not fully inflated, which is different from pneumonia, where the alveoli become inflamed and fill with fluid, hindering gas exchange. This condition may be caused by an obstruction preventing air from reaching parts of the lung, post-surgical complications, or other factors. It does not involve fluid in the alveoli as seen in pneumonia, which is often due to infection. Tuberculosis is a specific infectious disease that damages lung tissue but does not specifically relate to the concept of incomplete expansion. Epistaxis is unrelated as it refers to nosebleeds, and asthma involves inflammation and constriction of the airways, not the incomplete expansion of the alveoli itself.