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': 'Prominent left border of hea is formed by all the following except: \nSelect and explain. \nA. Azygous vein, B. Pericardial cyst, C. Coronary aery aneurysm, D. Enlarged left auricular aneurysm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Azygous vein', 'role': 'assistant'}]