$A$ block of mass $m$ is released from rest at point $A$ on an inclined plane of angle $\theta$ with the vertical. The block slides down and compresses a spring of spring constant $k$. Find the compression in the spring when the speed of the block is maximum.

• A
  $\frac{mg\sin \theta}{k}$
• B
  $\frac{2mg\sin \theta}{k}$
• C
  $\frac{mg\cos \theta}{k}$
• D
  $\frac{mg}{k}$