This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glomerular Filtration, Renal Blood Flow, and Their Control, Subject name: Physiology
Two substances that can probably be used to determine filtration fraction are - 
Select and explain. 
A. Insulin and mannitol, B. Urea anddiodrast, C. PAH and phenol red, D. Inulin and PAH
D: Inulin and PAH
Answer: D: Inulin and PAH 
Explanation: Ans. is 'd' i.e., Inulin and PAH o GFR is measured by inulin and renal plasma flow is measured by PAH.