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': 'Following is not a differential diagnosis for middle mediastinal mass \nSelect and explain. \nA. Tortuous innominate artery, B. Bronchogenic cyst, C. Aortic arch aneurysm, D. Neuro enteric cyst', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Neuroenteric cyst - Posterior mediastinum.', 'role': 'assistant'}]