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
Normal filtration fraction is around: 
Select and explain. 
A. 0.05, B. 0.1, C. 0.2, D. None of the above
C: 0.2
Answer: C: 0.2 
Explanation: The ratio of the GFR to the RPF, the filtration fraction, is normally 0.16 to 0.20. The GFR varies less than the RPF. When there is a fall in systemic blood pressure, the GFR falls less than the RPF because of efferent aeriolar constriction, and consequently the filtration fraction rises. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 38.