Woman with fever, productive cough, and shortness of breath

A 65-year old woman complains of recent onset right-sided chest pain, fever, productive cough with rust-colored sputum, and shortness of breath. Chest x-ray reveals an infiltrate in the right-middle lobe. A lung biopsy demonstrates alveolar spaces filled with neutrophils. Cultures are positive for Streptococcus pneumoniae. The patient is started on antibiotic therapy.

The most likely diagnosis is:

A. Acute viral pneumonia
B. Acute bacterial pneumonia
C. Hypersensitivity pneumonitis
D. Asthma
E. Chronic bronchitis