Choose the correct statements about emphysema.

(a) Alveolar walls are damaged.

(b) The number of alveoli increases.

(c) Respiratory surface area increases.

(d) Cigarette smoking is a major cause.

(a) Alveolar walls are damaged. - True. Emphysema is characterized by the destruction of alveolar walls, leading to enlarged air spaces and reduced surface area for gas exchange.

(b) The number of alveoli increases. - This statement is incorrect. In emphysema, the destruction of alveolar walls occurs, leading to the coalescence of adjacent alveoli and the formation of larger air spaces called bullae. As a result, the number of functional alveoli decreases rather than increases.

(c) Respiratory surface area increases. - This statement is incorrect. Emphysema results in the destruction of alveolar walls, which reduces the surface area available for gas exchange in the lungs. As a consequence, the respiratory surface area decreases, impairing the efficiency of gas exchange and leading to respiratory difficulties.

(d) Cigarette smoking is a major cause. - True. Cigarette smoking is a significant risk factor for developing emphysema, as it leads to chronic inflammation and damage to the lungs.