This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
A 28-year-old man presents with coughing up blood and sputum. He gives a history of recurrent pneumonias and a chronic cough productive of foul-smelling purulent sputum. He has no other past medical history and is a lifetime nonsmoker. On physical examination, there are no oral lesions, heart sounds are normal, and wet inspiratory crackles are heard at the lung bases posteriorly. He also has clubbing of his fingers, but there is no hepatosplenomegaly or any palpable lymph nodes. CXR show fibrosis and pulmonary infiltrates in the right lower lung. Which of the following is the most appropriate initial diagnostic test? 
Select and explain. 
A. chest CT scan, B. bronchoscopy, C. bronchography, D. open thoracotomy
A: chest CT scan
Answer: A: chest CT scan 
Explanation: Bronchography has been superseded by a CT scan in defining the extent of bronchiectasis. Occasionally, advanced cases of saccular bronchiectasis can be diagnosed by routine CXR. The use of high-resolution CT scanning, in which the images are 1.5 mm thick, has resulted in excellent diagnostic accuracy.