The velocity ($v$) – time ($t$) plot of the motion of a body is shown below. The graph starts from origin, increases linearly to a peak, then decreases linearly to zero velocity at a later time.

The acceleration ($a$) – time ($t$) graph that best suits this motion is:

Acceleration is the slope of the $v-t$ graph ($a=\frac{dv}{dt}$).In the first part, velocity increases linearly $\Rightarrow$ slope is positive and constant. Thus, $a$ is constant and positive.In the second part, velocity decreases linearly $\Rightarrow$ slope is negative and constant. Thus, $a$ is constant and negative.The $a-t$ graph will show a positive constant block followed by a negative constant block. This corresponds to option (3).