Which of the following velocity-time graphs shows a realistic situation for a body in motion?

The velocity $v$ of a particle is given by the equation $v = 6t^2 - 6t^3$,where $v$ is in $m/s$ and $t$ is time in $s$. Then:

If the position-time graph of a particle is a sine curve as shown,what will be its velocity-time graph?

Write the definition of instantaneous velocity.

The acceleration versus velocity graph of a particle moving in a straight line starting from rest is as shown in the figure. The corresponding velocity-time graph would be:

The speed-time graph of a particle moving along a fixed direction is shown in the figure. What is the average speed of the particle over the intervals: $(a)$ $t = 0\; s$ to $10\; s$,and $(b)$ $t = 2\; s$ to $6\; s$?