This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'All of the following are contents of middle mediastinum except \nSelect and explain. \nA. Phrenic nerve, B. Ascending aoa, C. Arch of aoa, D. Pulmonary aery', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Arch of aoa occupies in the superior mediastinum B D CHAURASIA&;S HUMAN ANATOMY UPPER LIMB THORAX-VOLUME 1 SIXTH EDITION Page no:246', 'role': 'assistant'}]