A 72-year-old smoker develops a left lower lobe pneumonia that is treated with a 5-day course of azithromycin. His symptoms and lobar infiltrate do not improve and he is admitted to the hospital for...

A 72-year-old smoker develops a left lower lobe pneumonia that is treated with a 5-day course of azithromycin. His symptoms and lobar infiltrate do not improve and he is admitted to the hospital for IV antibiotics. Upon further inquiry, he has also had blood-streaked sputum and lost 25 pounds over the past 2 months. Which of the following is a reasonable next test that will most likely yield a specific diagnosis?

A. CT scan of thorax

B. MRI of thorax

C. Bronchoscopy

D. Mediastinoscopy

E. Open biopsy