A block of mass m slides down an inclined plane which makes an angle $\theta$ with the horizontal. The coefficient of friction between the block and the plane is $\mathrm{\mu }$ . The force exerted by the block on the plane is

• A

  $\mathrm{mg} \cos \mathrm{\theta }$

• B

  $\sqrt{{\mathrm{\mu }}^2+1}.\mathrm{mgcos\theta }$

• C

  $\frac{\mathrm{\mu } \mathrm{mg} \cos \mathrm{\theta }}{\sqrt{{\mathrm{\mu }}^2+1}}$

• D

  $\mathrm{\mu } \mathrm{mg} \cos \mathrm{\theta }$