Consider a rubber ball freely falling from a height $$h = 4.9\,m$$   onto a horizontal elastic plate. Assume that the duration of collision is negligible and the collision with the plate is totally elastic.
Then the velocity as a function of time and the height as a function of time will be:

Solution :
For downward motion: $$v=-gt$$
The velocity of the rubber ball increases in downward direction and we get a straight line between $$v$$ and $$t$$ with a negative slope.
Also applying $$y - {y_0} = ut + \frac{1}{2}a{t^2}$$
We get $$y - h = - \frac{1}{2}g{t^2}\,\, \Rightarrow y = h - \frac{1}{2}g{t^2}$$
The graph between $$y$$ and $$t$$ is a parabola with $$y = h$$  at $$t= 0.$$   As time increases $$y$$ decreases.
For upward motion:
The ball suffer elastic collision with the horizontal elastic plate therefore the direction of velocity is reversed and the magnitude remains the same.
Here $$v=u-gt$$   where $$u$$ is the velocity just after collision. As $$t$$ increases, $$v$$ decreases. We get a straight line between $$v$$ and $$t$$ with negative slope.
Also $$y = ut - \frac{1}{2}g{t^2}$$
All these characteristics are represented by graph (B).