$A$ 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 the angle of inclination of the pendulum with the vertical is $\sin^{-1}\left(\frac{g}{a}\right)$
• B
  to the left and the angle of inclination of the pendulum with the vertical is $\tan^{-1}\left(\frac{a}{g}\right)$
• C
  to the left and the angle of inclination of the pendulum with the vertical is $\sin^{-1}\left(\frac{a}{g}\right)$
• D
  to the left and the angle of inclination of the pendulum with the vertical is $\tan^{-1}\left(\frac{g}{a}\right)$