A horizontal platform is made to execute SHM of amplitude a in the vertical direction. An object placed on the platform will lose contact with it, when the frequency of oscillation exceeds:

• A

  $\frac{1}{\mathrm{\pi }}\sqrt{\frac{\mathrm{g}}{\mathrm{a}}}$

• B

  $\frac{1}{2\mathrm{\pi }}\sqrt{\frac{\mathrm{g}}{\mathrm{a}}}$

• C

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{g}}{\mathrm{a}}}$

• D

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{a}}{\mathrm{g}}}$