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: Pathology
[{'content': 'Clinical feature of CRF appear when renal function is reduce to - \nSelect and explain. \nA. 70%, B. 50%, C. 30%, D. 20% of normal', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]