An Emergency Medical Responder asks you to explain a pneumothorax. You would explain that a pneumothorax occurs when:

A) the lung becomes overinflated with air and collapses.
B) air accumulates around the lung, causing a portion of it to collapse.
C) the trachea becomes obstructed, causing the lungs to collapse.
D) air enters the lung and alveoli from a traumatic opening in the chest wall.

B