Consider the motion of the tip of the minute hand of a clock. In one hour
a) the displacement is zero
b) the distance covered is zero
c) the average speed is zero
d) the average velocity is zero

In a trip of one hour of a tip of the minute hand, its initial and final positions are the same. Displacement is the distance between the initial and final position Thus, its displacement in this trip is zero. Option A is correct.
But it has covered some path in this trip, thus distance traveled by the tip of the hand is not zero. Thus, the Average speed that is defined as the ratio of total distance travelled with the total time taken is not zero. Options B and C are incorrect.
Also, the average velocity is defined as the ratio of total displacement with the total time taken, as displacement is zero, the average velocity of the tip also remains zero. Option D is correct.