What does the area of $v-t$ graph of a moving object represent?

Draw the $x-t$ graphs which represent positive,negative,and zero velocity.

The displacement $x$ versus time graph is shown below. Analyze the following statements:
$(A)$ The average velocity during $0$ to $3\ s$ is $10\ m/s$.
$(B)$ The average velocity during $3$ to $5\ s$ is $0\ m/s$.
$(C)$ The instantaneous velocity at $t = 2\ s$ is $5\ m/s$.
$(D)$ The average velocity during $5$ to $7\ s$ and instantaneous velocity at $t = 6.5\ s$ are equal.
$(E)$ The average velocity from $t = 0$ to $t = 9\ s$ is zero.
Choose the correct answer from the options given below.

What is common in the two graphs given below?

The maximum possible acceleration of a train moving on a straight track is $10\ m/s^2$ and the maximum possible retardation is $5\ m/s^2$. If the maximum achievable speed of the train is $10\ m/s$,then the minimum time in which the train can complete a journey of $135\ m$ starting from rest and ending at rest is.........$s$.

$A$ train starting from rest accelerates uniformly for $100\,s,$ then comes to a stop with a uniform retardation in the next $200\,s.$ During the motion,it covers a distance of $3\,km.$ Choose the wrong option.