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 lie between the 1st rib and the apex of the lung, except \nSelect and explain. \nA. Thoracic duct, B. Superior intercostal aery, C. First posterior intercostal vein, D. Sympathetic trunk', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Thoracic duct is in the posterior mediastinum . <img src=" /> Ref - BDC 6th editon vol 1 Pg275', 'role': 'assistant'}]