Something that accelerates undergoes a A. Change in velocity per unit time
B. Change in direction
C. Change.
D. Change in velocity

Change in velocity per unit time.

Explanation

Acceleration is defined as rate of change of velocity w.r.t time.

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers

we need to know the time interval during which the force acts. impulse of force = momentum change