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': 'Left renal vein crosses aorta - \nSelect and explain. \nA. Posterior at level of superior mesenteric artery, B. Anterior above the level of superior mesenteric artery, C. Anterior below the superior mesenteric artery, D. Anterior below the inferior mesenteric artery', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Left renal vein passes behind and below the superior mesenteric artery, crossing in front of the aorta.', 'role': 'assistant'}]