Asthma is primarily characterized by which of the following?

Asthma is primarily characterized by episodes of severe breathing difficulty due to inflammation and narrowing of the airways in the lungs. This condition leads to symptoms such as wheezing, shortness of breath, chest tightness, and coughing, particularly during the night or early morning. The mechanism behind asthma involves bronchoconstriction, airway inflammation, and increased mucus production, which can be triggered by various factors such as allergens, respiratory infections, physical activity, and irritants.

The other options describe different medical conditions that are unrelated to asthma. Enlargement of the prostate gland pertains to benign prostatic hyperplasia, which affects the urinary system, while the formation of cysts in the ovaries relates to polycystic ovary syndrome, a reproductive health issue. Fluid accumulation in the bladder is associated with various urinary disorders but does not connect to asthma's respiratory characteristics. Therefore, the correct answer accurately reflects the distinctive features of asthma.