$A$ block of mass $m$ is stationary on a rough plane of mass $M$ inclined at an angle $\theta$ to the horizontal,while the whole setup is accelerating upwards at an acceleration $a$. If the coefficient of friction between the block and the plane is $\mu$,then the force that the plane exerts on the block is

• A
  $m(g+a)$ upwards
• B
  $m g \cos \theta$ normal to the plane
• C
  resultant of $m g \cos \theta$ normal to the plane and $\mu m g \cos \theta$ along the plane
• D
  resultant of $m(g+a) \cos \theta$ normal to the plane and $\mu m(g+a) \cos \theta$ along the plane