A Toy gun has a spring of force constant ,k. After changing the spring by compressing it through a distance of & the toy releases a shot of mass m vertically upwards. Then the shot will travel a vertical height is equal to

• A

  $\frac{2\mathrm{mg}}{{\mathrm{kx}}^2}$

• B

  $\frac{{\mathrm{kx}}^2}{\mathrm{mg}}$

• C

  $\frac{\mathrm{kx}}{\mathrm{mg}}$

• D

  $\frac{{\mathrm{kx}}^2}{2\mathrm{mg}}$