A block of mass m is at rest on an inclined plane which is making angle $\theta$ with the horizontal. The coefficient of friction between the block and plane is  $\mu$. Then, frictional force acting between the surfaces is 

• A

  $\mu$ mg

• B

  $\mu$  mg sin $\theta$

• C

  $\mu$ (mg sin $\theta$ - mg cos $\theta$)

• D

  mg sin $\theta$