This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidneys and Body Fluids, Subject name: Physiology
[{'content': 'Substance ideal for GFR estimation is? \nSelect and explain. \nA. Inulin clearance, B. PAH clearance, C. Urea clearance, D. All of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (Inulin clearance)^/: Ganong, 22nd ed,p. 706GFR can be measured in intact experimental animals and humans by measuring the excretion and plasma level of a substance that is freely filtered through the glomeruli and neither secreted nor reabsorbed in the tubules.Inulin is a polymer of fructose with a molecular weight of 5200 obtained from Dahlia tubers, meets the above criterion and is extensively used to measure GFR.Remember Ideal substance to measure GFR-InulinSubstance used for practical purposes-CreatinineSubstance used to measure renal blood flow-PAHNormal GFR of human beings-125 ml/min ClearanceCx=UVP=Urine concentrationsne flow/time (V)Plasma concentration.', 'role': 'assistant'}]