One of the major challenges of chronic bronchitis is:

Chronic bronchitis is characterized by inflammation of the bronchial tubes and an increase in mucus production, which can lead to significant airway obstruction. One of the major challenges associated with this condition is the frequent occurrence of respiratory infections. The compromised airways and increased mucus create an environment conducive to bacterial growth, making individuals more susceptible to infections such as pneumonia and bronchitis exacerbations.

Additionally, the persistent inflammation and mucus buildup can impair normal lung function, hindering the body's ability to clear pathogens effectively. This can further escalate the severity and frequency of respiratory infections, leading to a cycle of illness that significantly impacts a person's health and quality of life.

In contrast, the other options do not accurately represent the challenges faced by individuals with chronic bronchitis. Increased exercise tolerance is generally not associated with chronic bronchitis, as patients often experience shortness of breath with physical activity. Excessive lung capacity is also not a feature of chronic bronchitis; rather, lung function is typically diminished. Finally, voluntary airway constriction is not a characteristic challenge of the disease process in chronic bronchitis; this term would be more relevant in discussions of asthma.