$A$ dimensionally consistent relation for the volume $V$ of a liquid of coefficient of viscosity $\eta$ flowing per second through a tube of radius $r$ and length $l$ and having a pressure difference $p$ across its end,is

• A
  $V = \frac{\pi p r^4}{8 \eta l}$
• B
  $V = \frac{\pi \eta l}{8 p r^4}$
• C
  $V = \frac{8 p \eta l}{\pi r^4}$
• D
  $V = \frac{\pi p \eta}{8 l r^4}$