A. Acceleration $=\mathrm{ }$ constant; $\mathrm{a}\mathrm{ }\mathrm{v}\to \mathrm{t}$ graph will be constant line parallel to time axis. Option $\left(\mathrm{A}\right)$ is correct.
B. $\mathrm{v}=\mathrm{u}+\mathrm{a}\mathrm{t}$ ; velocity vs time graph will be straight line passing through origin. Option $\left(\mathrm{B}\right)$ is correct.
$\mathrm{u}=0;\mathrm{ }$ initially at rest
$\mathrm{v}=$ at
C. $\mathrm{X}=\frac{1}{2}\mathrm{a}{\mathrm{t}}^2$ (particle was initially at origin) $\mathrm{v}\to \mathrm{t}$ graph will be parabola passing through origin. Option $\left(\mathrm{D}\right)$ is correct.