Answer:
the answer is 
Step-by-step explanation:
constant acceleration 
 
because when the object's velocity is changing then the object is accelerating or decelerating 
as acceleration describe changing of velocity so the answer is constant acceleration
Acceleration is defined as the rate of change of velocity. 
 
Acceleration = (Change in velocity) / time taken 
 
Acceleration = (Final velocity - initial velocity) / time 
 
As the object velocity changes by the same amount in each second, it means the acceleration is constant. 
 
Hope I can help u