This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Best diagnostic aid for broncheitasis is: \nSelect and explain. \nA. Bronchoscopy, B. X- Ray, C. Bronchography, D. CT Scan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. CT Scan', 'role': 'assistant'}]