Which change most directly explains why alveolar damage can reduce gas exchange?

### Why this is right Alveoli are small air sacs involved in gas exchange. The material states that smoking can damage alveoli, destroy their walls, and reduce elasticity, making gas exchange less effective. ### The concept Gas exchange is the movement of oxygen into the blood and carbon dioxide out of it. Healthy alveolar structure supports this exchange. When alveolar walls are damaged, the lung's ability to exchange gases is reduced. Loss of elasticity also makes it harder for the lungs to expand and contract normally. These changes can contribute to breathlessness and fatigue during exertion. ### The other options - **B. Increased ciliary movement**: The material identifies ciliary dysfunction as an effect of smoke, not increased ciliary movement as the cause of alveolar gas-exchange loss. - **C. Reduced exposure to smoke**: This is a preventive action, not a cause of alveolar damage. - **D. Improved airway clearance**: This would not explain damage to alveolar walls and is not described as a smoking effect. ### Terms - **Alveoli**: Small air sacs in the lungs where oxygen and carbon dioxide are exchanged. - **Gas exchange**: The movement of oxygen into the blood and carbon dioxide out of the blood. - **Elasticity**: The ability of lung tissue to stretch and return toward its original shape. ### Remember Airway narrowing affects airflow; alveolar wall damage affects the lungs' gas-exchange surface.