Final answer:
Speed is a scalar quantity that measures how fast an object changes its location, disregarding the direction of motion. It is incorrectly identified in the options provided, but is closely related to the rate of change of velocity with respect to time, considering only magnitude.
Step-by-step explanation:
The correct definition to match the term speed is the rate at which an object changes its location. In physics, speed is defined as a scalar quantity, which means it has magnitude but no direction associated with it. Unlike velocity, which is a vector and includes both magnitude and direction, speed only concerns itself with how fast an object is moving.
Therefore, using the provided information, we can deduce that the appropriate definition for speed would be none of the given options directly. However, it is closely related to 'The rate of change of velocity with respect to time' if we consider only the magnitude aspect of velocity. The calculation for average speed involves dividing the total distance traveled by the total time taken, without considering the direction of motion.