Since total displacement total distance, magnitude of average velocity is never less than the average speed of a particle in the given time. Therefore, option A is correct.

It is possible to have a situation in which and . Such situation occurs in Uniform Circular Motion where the velocity is constant but its direction is always changing. Hence acceleration exists. Therefore, option B is correct.

The displacement of a particle performing Uniform Circular Motion is zero in one revolution. Hence average velocity is zero in this time interval while the instantaneous velocity is never zero in this time interval. Therefore, option C is correct.

Average velocity of a particle in a straight line is never zero if we consider some value of displacement in the given time interval. Hence option D is not correct.