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
A "Vascular Ring" causing external airway compression can be diagnosed by: 
Select and explain. 
A. CT, B. PET CT, C. MRI, D. Angiography of aoic and pulmonary circulation
D: Angiography of aoic and pulmonary circulation
Answer: D: Angiography of aoic and pulmonary circulation 
Explanation: Angiography of aoic and pulmonary circulation