This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chronic Kidney Disease & Diabetic Nephropathy, Subject name: Medicine
[{'content': 'Clinical features of C.R.F begin to appear when renal function is reduced to: \nSelect and explain. \nA. 70%, B. 50%, C. 30%, D. 20%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Stage 1 and 2 of CKD are asymptomatic Symptoms beginning in Stage 3. Stage 3 begins at GFR of < 60ml/ min/ 1.73m2 body surface area. Clinical features of CRF will develop when >50% or more of kidney parenchyma is destroyed. Renal injury , kidney has innate ability to maintain GFR-remaining healthy nephrons manifest hyperfiltration and compensatory hyperophy. This nephron adaptability allows for continued normal clearance of plasma solutes. The Plasma levels of substances such as urea and creatinine sta to show measurable increases only after total GFR has decreased to 50%.', 'role': 'assistant'}]