This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
Investigation of choice for bronchiectasis 
Select and explain. 
A. Alpha 1-antitrypsin level, B. ANCA, C. Ds-DNA, D. CT
D: CT
Answer: D: CT 
Explanation: Chest CT is more specific for bronchiectasis and is the imaging modality of choice for confirming the diagnosis.CT findings include airway dilation(tram track or signet ring sign),lack of bronchial tapering,bronchial wall thickening in dilated airways,inspissated secretions or cysts emanating from the bronchial wall Ref:Harrison's med:18th edition,page no:2143.