$A$ body can have zero average velocity but not zero average speed. Justify this statement by giving an example.

(N/A) Average velocity is defined as the total displacement divided by the total time taken. Since displacement is a vector quantity,if an object returns to its starting point,the total displacement becomes $0$,resulting in an average velocity of $0$.
Average speed is defined as the total distance traveled divided by the total time taken. Since distance is a scalar quantity and represents the total path length,it cannot be $0$ for a moving object.
Example: Consider an object moving along a circular path of radius $r$. If the object completes one full revolution,the total displacement is $0$,so the average velocity is $0$. However,the total distance traveled is equal to the circumference of the circle,which is $2 \pi r$. Thus,the average speed is $\frac{2 \pi r}{t}$,where $t$ is the time taken.