The correct answer is d) acceleration.
Acceleration refers to the rate at which an object’s velocity changes over a specific period of time. When an object speeds up, slows down, or changes direction, it is experiencing acceleration. In contrast, instantaneous velocity is the velocity of an object at a specific moment in time, while speed is the magnitude of velocity without considering direction. Therefore, among the given options, acceleration is the only term that accurately describes the rate of change in velocity.