Two balls A and B are thrown with speeds u and u/2, respectively. Both the balls cover the same horizontal distance before returning to the plane of projection. If the angle of projection of ball B is 15° with the horizontal, then the angle of projection of A is

• A

  ${\sin }^{-1}\left(\frac{1}{8}\right)$

• B

  $\frac{1}{2}{\sin }^{-1}\left(\frac{1}{-8}\right)$

• C

  $\frac{1}{3}{\sin }^{-1}\left(\frac{1}{8}\right)$

• D

  $\frac{1}{4}{\sin }^{-1}\left(\frac{1}{8}\right)$