A smooth square platform ABCD is moving towards right with a uniform speed v.  At what angle $\mathrm{\theta }$  must a particle be projected from A with speed u so that it strikes the point B.  
 

• A

  ${\sin }^{-1}\left(\frac{\mathrm{u}}{\mathrm{v}}\right)$

• B

  ${\cos }^{-1}\left(\frac{\mathrm{v}}{\mathrm{u}}\right)$

• C

  ${\cos }^{-1}\left(\frac{\mathrm{u}}{\mathrm{v}}\right)$

• D

  ${\sin }^{-1}\left(\frac{\mathrm{v}}{\mathrm{u}}\right)$