a) η=\(\frac{πpr^4 t}{8Vl} \)
b) η=\(\frac{πpr^4 t}{16Vl} \)
c) η=\(\frac{πpr^4 t}{32Vl} \)
d) η=\(\frac{3πpr^4 t}{8Vl} \)

Answer: a
Explanation: Poiseuille’s law is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section.
Formula for Poiseuille’s law is: η=\(\frac{πpr^4 t}{8Vl} \)