Under what conditions is the average velocity equal to the instantaneous velocity?

Question

$\begin{array}{1 1} (a)\; \text{when there is uniform motion of the body in one dimension} \\ (b)\; \text{when there is non-uniform motion in one dimension } \\ (c)\; \text{when there is uniform motion in two dimensions } \\ (d)\; \text{when there is non-uniform motion in two dimensions} \end{array}$