What is the nature of the displacement-time graph of a body moving with constant velocity?

The speed-time graph of a body is a straight line parallel to the time axis. The body has:

State which of the following situations are possible and give an example of each of these:
$(a)$ $A$ body moving with constant acceleration but with zero velocity.
$(b)$ $A$ body moving horizontally with an acceleration in the vertical direction.
$(c)$ $A$ body moving with a constant speed in an accelerated motion.

What is meant by free fall? Two bodies,one of mass $1\,g$ and other of mass $1\,kg$,are dropped from the same height in a vacuum. Compare the two time intervals in which the two bodies will hit the ground.

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.

How can you find the following?
$(i)$ Velocity from a displacement-time graph.
$(ii)$ Acceleration from a velocity-time graph.
$(iii)$ Displacement from a velocity-time graph.
$(iv)$ Velocity from an acceleration-time graph.