Which of the following conditions is characterized by airflow limitation that is not fully reversible?

Chronic bronchitis is characterized by airflow limitation that is not fully reversible due to long-term inflammation and irritation of the airways, primarily caused by smoking or prolonged exposure to irritants. In chronic bronchitis, the airways become narrowed and clogged with mucus, leading to a persistent cough and difficulty in breathing. This airflow limitation can worsen over time and is often associated with irreversible changes in the airflow pathways, such as airway remodeling and damage to lung tissue.

In contrast, asthma is typically marked by reversible airflow limitation, meaning that symptoms can improve with the use of bronchodilators or other medications. Obstructive sleep apnea involves intermittent blockage of the upper airway during sleep and does not directly cause airflow limitation in the same manner as chronic bronchitis. Restrictive lung disease encompasses a range of conditions that limit lung expansion and reduce total lung capacity, which is a different mechanism affecting airflow.

Therefore, chronic bronchitis stands out for its characteristic non-reversible airflow limitation, making it the correct answer.