A coin is placed on a horizontal platform which undergoes vertical simple harmonic motion of angular frequency $\mathrm{\omega }$ The amplitude of oscillation is gradually increased. The coin will leave contact with the platform for the first time

• A

  at the mean position of the platform

• B

  for an amplitude of $\mathrm{g}/{\mathrm{\omega }}^2$

• C

  for an amplitude of ${\mathrm{g}}^2/{\mathrm{\omega }}^2$

• D

  at the highest position of the platform