The coefficient of viscosity  of a liquid can be defined from the equation $\mathrm{F}=\mathrm{\eta A}(\mathrm{dv}/\mathrm{dx})$where F is the tangential force  between two liquid layers of area A. The layers are at a distance dy apart and du is the difference in their velocities. 
Suitable unit for dv/dx is:

• A

  $m s^{-1}$

• B

  ${\mathrm{s}}^{-1}$

• C

  ${\mathrm{Nm}}^{-2}$

• D

  ${\mathrm{N}}^{-1}{\mathrm{m}}^2$