The graph between the displacement x and time t for a particle moving in a straight line is shown in figure. During the interval $OA,\text{\hspace{0.17em}}AB,\text{\hspace{0.17em}}BC$ and CD, the acceleration of the particle is

 OA AB BC CD (1) + 0 + + (2) – 0 + 0 (3) + 0 – + (4) – 0 – 0