Let velocity is positive. So the acceleration is negative according to given data. This means that acceleration is less than zero. This is only possible when final velocity is less than initial velocity. Thus, we say the particle is slowing down. We can also take the vice-versa case.

Let position is in positive direction. So the velocity is in negative direction according to the given data. This means that the particle is moving back towards origin. We can also take vice-versa case.

If the velocity is zero at the instant, it does not mean that the change in velocity is zero. Thus the acceleration may not be zero at that instant.

If the velocity is zero for a time interval, it means that the change in velocity is zero in this time interval. Thus the acceleration is zero at any instant within this time interval.

Therefore, options A, B and D are correct.