A.accelerating
Explanation:
Acceleration is defined as the ratio between the change in velocity and the time taken for the velocity to change:
We must note that the velocity is a vector - so it has both a magnitude (the speed) and a direction.
This means that a non-zero acceleration occurs when:
- the speed changes, or
- the direction changes, or
- both the speed and the direction change
For an object moving at constant speed in a circle, the direction changes, so the object is accelerating.