Turpentine oil is flowing through a tube of length $l$ and radius $r$. The pressure difference between the two ends of the tube is $P .$ The viscosity of oil is given by $\eta=\frac{P\left(r^{2}-x^{2}\right)}{4 v l}$ where $v$ is the velocity of oil at a distance $x$ from the axis of the tube. The dimensions of $\eta$ are

• A

  $\left[ {M{L}{T^{ - 1}}} \right]$

• B

  $\left[ M^0L^0T^0 \right]$

• C

  $\left[ {M{L^{ - 1}}{T^{ - 1}}} \right]$

• D

  $\left[ {M{L^{ 2}}{T^{ - 2}}} \right]$