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.

The distance-time graph below represents the motion of two buses $A$ and $B$.
$(i)$ What is the distance by which bus $B$ was ahead of bus $A$ initially?
$(ii)$ Do they ever meet each other? If so,when?
$(iii)$ What is the distance travelled by bus $A$ when it overtakes bus $B$?
$(iv)$ Find out the distance by which bus $A$ was ahead of bus $B$ at $t = 12 \ h$.
$(v)$ Which one of them is moving faster? Give reason.

The velocity-time graph of a truck is plotted below.
$(a)$ Calculate the magnitude of displacement of the truck in $15$ seconds.
$(b)$ During which part of the journey was the truck decelerating?
$(c)$ Calculate the magnitude of average velocity of the truck.

The area under a $v-t$ graph represents a physical quantity which has the unit:

The distance$-$time graph of a body is parallel to the time axis. The body is

What kind of motion of a body is represented by the graphs given below?