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: Unknown
Poiseuille’s hagen lawis 
Select and explain. 
A. F = (PA–PB) × 3.14 × r4/8nl, B. F = (PA+PB) × 3.14 × r4/8nl, C. F = (PA/PB) × 3.14 × r4/8nl, D. F = (PA × PB) × 3.14 × r4/8nl
A: F = (PA–PB) × 3.14 × r4/8nl
Answer: A: F = (PA–PB) × 3.14 × r4/8nl 
Explanation: Poiseuille-Hagen Formula
The relation between the flow in a long narrow tube, the viscosity of the fluid, and the radius of the tube is expressed mathematically in the Poiseuille-Hagen formula: