$A$ vertical spring with force constant $k$ is fixed on a table. $A$ ball of mass $m$ at a height $h$ above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance $d$. The net work done in the process is

• A
  $mg(h + d) - \frac{1}{2}kd^2$
• B
  $mg(h - d) - \frac{1}{2}kd^2$
• C
  $mg(h - d) + \frac{1}{2}kd^2$
• D
  $mg(h + d) + \frac{1}{2}kd^2$