Which of the following best describes COPD?

Chronic Obstructive Pulmonary Disease (COPD) is primarily characterized by airflow obstruction, leading to an inability to fully exhale air from the lungs. One of the hallmark features of COPD is that air becomes trapped in the lungs due to narrowed airways and compromised lung function. This trapping of air occurs particularly during exhalation.

As the disease progresses, the damage to the airways and lung tissue, often due to long-term exposure to irritants such as smoke or pollution, leads to a decrease in the ability of the lungs to expel air, which results in increased residual volume. This means that even after exhalation, a significant volume of air remains in the lungs, leaving the individual with less capacity for fresh air intake.

This characteristic clearly aligns with the definition and understanding of COPD, making it the most accurate description among the options provided. It emphasizes the obstructive nature of the disease rather than the elasticity of the lungs or any specific respiratory volume measurements.