This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
The signs and symptoms of CRF are seen from what stage of renal deterioration - 
Select and explain. 
A. GFR-90ml/min/1.73m2, B. GFR-70ml/min/1.73m2, C. GFR-45ml/min/1.73m2, D. GFR-80ml/min/1.73m2
C: GFR-45ml/min/1.73m2
Answer: C: GFR-45ml/min/1.73m2 
Explanation: Ref:Harrison 20 th edition pg no 2112 The classification of chronic kidney disease -based on GFR G1 Normal or high >or equal to 90ml/min/1.73m2 G2 mildly decreased 60-89 G3a mildly to moderately decreased 45-59 G3b moderately to severely decreased 30-44 G4 severely decreased 15-29 G5 Kidney failure <15 Ref Harrison20th edition pg 289