This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Pathology
[{'content': 'Percentage of renal vein involvement in renal cell carcinoma is - \nSelect and explain. \nA. 2%, B. 8%, C. 16%, D. 32%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 8% Renal cell carcinoma with renal vein and inferior vena cava involvement Ref:', 'role': 'assistant'}]