If the displacement $-$ time graph for a particle is parallel to the time axis, what is the velocity of the particle?

What does the slope of a displacement$-$time graph represent? Can a displacement$-$time graph be parallel to the displacement axis? Give a reason for your answer.

$A$ driver of a car travelling at $52\, km\, h^{-1}$ applies the brakes and accelerates uniformly in the opposite direction. The car stops in $5\, s$. Another driver going at $3\, km\, h^{-1}$ in another car applies his brakes slowly and stops in $10\, s$. On the same graph paper,plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?

Name the physical quantities denoted by:
$(i)$ The slope of the distance$-$time graph.
$(ii)$ The area under a velocity$-$time graph.
$(iii)$ The slope of a velocity$-$time graph.

Identify what the graphs shown below indicate.

What conclusion can you draw from the displacement$-$time graph of a body as shown below?