How does pneumonia primarily affect the lungs?

Pneumonia primarily affects the lungs by causing inflammation in the air sacs, or alveoli, which leads to the accumulation of fluid or pus. This build-up can significantly impair the lungs' ability to exchange oxygen and carbon dioxide effectively. When the air sacs fill with fluid or pus, it creates a blockage that not only makes breathing difficult but can also cause symptoms such as cough, fever, and chest pain. This process is a hallmark of pneumonia and distinguishes it from other pulmonary conditions, as the infection directly disrupts the normal air exchange process in the lungs.

Injury to lung tissue due to inflammation and infection further complicates the situation, making option B the most accurate description of pneumonia's primary impact. Other options, while potentially describing associated conditions, do not accurately capture the fundamental changes occurring in the lungs as a result of pneumonia.