The correct answer is emphysema.
Emphysema is the enlargement of air sacs in the lungs.
It is a long-term, progressive disease of the lungs that primarily causes shortness of breath. People who have emphysema, their air sacs in the lungs (alveoli) is damaged. Over a period of time, the inner walls of the air sacs weaken and rupture creating larger spaces instead of many small ones. Normally, the lung tissue holds these small airways called bronchioles, open, allowing air to leave the lungs on exhalation. However, when the lung tissue is damaged like in the case of emphysema, these airway collapse, making it difficult for the lungs to empty and the air (gases) becomes trapped in the alveoli thus causing impaired gas exchange.
