A container containing water has a constant acceleration 'a' in the horizontal direction. Free surface of water gets sloped with the horizontal at angle:

• A

  ${\mathrm{COS}}^{-1}\left(\frac{\mathrm{g}}{\mathrm{a}}\right)$

• B

  ${\sin }^{-1}\left(\frac{\mathrm{g}}{\mathrm{a}}\right)$

• C

  ${\tan }^{-1}\left(\frac{\mathrm{a}}{\mathrm{g}}\right)$

• D

  ${\sin }^{-1}\left(\frac{\mathrm{a}}{\mathrm{g}}\right)$