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': 'All the structures are seen in transverse section at T4 veebral level except: \nSelect and explain. \nA. Arch of aoa, B. Thymus, C. Azygous vein, D. Thoracic duct', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Azygous vein', 'role': 'assistant'}]