Question

what is atelectasis?
enlargement of air spaces in the lungs
inflammation of lung tissue
accumulation of fluid in the lungs
collapse of lung tissue

Explanation:

Atelectasis is defined as the collapse of lung tissue. Enlargement of air spaces in the lungs is related to emphysema. Inflammation of lung tissue is characteristic of pneumonia. Accumulation of fluid in the lungs is called pulmonary edema.

Answer:

Collapse of lung tissue