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: Anatomy
[{'content': 'The structure found in a cross-section of the thorax at T4 veebra is : \nSelect and explain. \nA. Azygos vein, B. Brachiocephalic aery, C. Arch of the aoa, D. Left Subclan aery', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Arch of aoa', 'role': 'assistant'}]