Which of the following speed-time $(v-t)$ graphs is physically not possible?

The graph shows the variation with time $t$ of velocity $v$ of an object moving along a straight line. The $a-t$ graph will be:

The variation of velocity of a particle moving along a straight line with time is illustrated in the following figure. The distance travelled by the particle in $4 \, s$ is: (in $, m$)

$A$ particle of mass $m$ is constrained to move on the $x$-axis. $A$ force $F$ acts on the particle. $F$ always points toward the position labeled $E$. For example,when the particle is to the left of $E$,$F$ points to the right. The magnitude of $F$ is a constant $F_0$ except at point $E$ where it is zero. The system is horizontal. $F$ is the net force acting on the particle. The particle is displaced a distance $A$ towards the left from the equilibrium position $E$ and released from rest at $t = 0$. The velocity-time graph of the particle is:

Find the acceleration of the particle at $x = 5\,m$ using the given $v^2-x$ graph,where $v$ is velocity and $x$ is displacement.

If the velocity-time graph has the shape $AMB$,what would be the shape of the corresponding acceleration-time graph?