Which disease is primarily characterized by reversible airway obstruction?

Asthma is the disease primarily characterized by reversible airway obstruction. This condition results from inflammation, bronchoconstriction, and increased mucus production, leading to difficulty in breathing. The hallmark of asthma is the ability to reverse this obstruction, typically through the use of bronchodilators or naturally, over time, as the precipitating factors are resolved.

In asthma, episodes of wheezing, coughing, and shortness of breath can occur due to triggers such as allergens, exercise, or irritants, but these symptoms can improve significantly with treatment. The reversibility is crucial because it differentiates asthma from other respiratory conditions like chronic bronchitis or emphysema, where airway obstruction tends to be more permanent and progressive.

Pneumonia, on the other hand, is an infection that primarily affects the lungs, causing consolidation and impaired gas exchange, but it does not primarily feature reversible airway obstruction as a defining characteristic. Understanding the nature of these conditions helps clarify why asthma is the correct choice in this context.