Which of the following describes a bacterial infection of the lungs?

The answer is pneumonia, as it specifically refers to an infection that occurs in the lungs, typically caused by bacteria, viruses, or fungi. In the case of bacterial pneumonia, the infection leads to inflammation of the air sacs (alveoli) in one or both lungs, which can fill with fluid or pus, causing symptoms such as cough, fever, chills, and difficulty breathing. This distinct clinical picture is what sets pneumonia apart from other respiratory conditions.

Asthma primarily involves chronic inflammation and constriction of the airways and is not an infection. Bronchitis, while it can be caused by infections, often refers to inflammation of the bronchial tubes and may not be limited to an infectious cause. Pharyngitis pertains to inflammation of the throat, which also does not directly involve the lungs. Thus, pneumonia clearly stands out as the condition that describes a bacterial infection affecting the lungs.