The graph represents that displacement is increasing non-uniformly with time. Therefore, the velocity of the body is not constant, it's increasing and the body has an acceleration.

For example, velocity at A is
$\frac{\mathrm{BC}}{\mathrm{DC}}=\frac{(8-2)\mathrm{m}}{(3-1)\mathrm{s}}=\frac{6}{2}=3 \mathrm{m}/{\mathrm{s}}^{-1}$