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 that does not cross the midline is - \nSelect and explain. \nA. Left gonadal vein, B. Left renal vein, C. Left branchiocephalic vein, D. Hemiazygos vein', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In the left side, inferior phrenic vein, suprarenal vein, and the gonadal vein drains into left renal vein, whereas on the right side, they drain into inferior vena cava directly. So they do not cross the midline on the left side.', 'role': 'assistant'}]