A block A of mass M rests on a wedge B of mass 2M and inclination $\theta$. There is sufficient friction between A and B, so that A does not slip on B. If there is no friction between B and ground, the compression in spring is

• A

  $\frac{Mg\cos \theta }{k}$

• B

  $\frac{Mg\cos \theta \sin \theta }{k}$

• C

  $\frac{Mg\sin \theta }{k}$

• D

  zero