This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CVS Embryology, Subject name: Anatomy
[{'content': 'A 78-year-old patient presents with an advance cancer in the posterior mediastinum. The surgeons are in a dilemma as to how to manage the condition. Which of the following structures is most likely damaged? \nSelect and explain. \nA. Brachiocephalic veins, B. Arch of the azygos vein, C. Trachea, D. Hemiazygos vein', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The hemiazygos vein is in the posterior mediastinum. The brachiocephalic veins, trachea, and arch of the aoa are in the superior mediastinum, whereas the arch of the azygos vein is found in the middle mediastinum.', 'role': 'assistant'}]