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
In a normal individual, filtration fraction varies from: 
Select and explain. 
A. 0.16 - 0.20, B. 2.0 - 4.0, C. 0.5 - 0.7, D. 0.9 - 1.1
A: 0.16 - 0.20
Answer: A: 0.16 - 0.20 
Explanation: The ratio of the glomerular filtration rate (GFR) to the renal plasma flow (RPF), the filtration fraction, is normally 0.16-0.20. 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: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 37. Renal Function & Micturition. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.