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: Physiology
Best test for GFR is with: 
Select and explain. 
A. Inulin, B. Hippuric acid, C. Creatinine, D. PAH
A: Inulin
Answer: A: Inulin 
Explanation: A i.e. Inulin (Measurement of GFRGFR can be measured by measuring the excretion & plasma level of a substance that is freely filtered through glomeruli and neither secreted not reabsorbed by the tubulesQ.Requirement of substances used to measure GFR- Substances used- Filtered freely- Inulin (standard)Q- Neither reabsorbed, nor secreted by tubules- Creatinine- Nontoxic - Not metabolized by body.