A truck is stationary and has a bob suspended by a light string, in a frame attached to the truck. The truck suddenly moves to the right with an acceleration of a. The pendulum will tilt

• A

  to the left and angle of inclination of the pendulum with the vertical is ${\tan }^{-1}\left(\frac{\mathrm{g}}{\mathrm{a}}\right)$

• B

  to the left and angle of inclination of the pendulum with the vertical is ${\sin }^{-1}\left(\frac{\mathrm{g}}{\mathrm{a}}\right)$

• C

  to the left and angle of inclination of the pendulum with the vertical is ${\tan }^{-1}\left(\frac{\mathrm{a}}{\mathrm{g}}\right)$

• D

  to the left and angle of inclination of the pendulum with the vertical is ${\sin }^{-1}\left(\frac{\mathrm{a}}{\mathrm{g}}\right)$