The object that is accelerating is the hockey puck.
Explanation:
Acceleration doesn’t necessarily mean getting faster it just means a progressive change in speed. So, either speeding up or slowing down. Therefore the hockey puck is slowing down meaning it has a negative acceleration. It cannot be the first one because if it’s not in motion it’s not accelerating, it cannot be the soccer ball because it’s moving at a constant speed which is why the unit is m/s because it’s saying it’s moving at a constant speed of 3 m/s so therefore since it’s constant it’s not getting any faster or slower so no acceleration, and then the last one is just describing a displacement so it’s not acceleration.