Answer:
d. all motion is relative.
Step-by-step explanation:
It is important to define a frame of reference because all motion is relative to a particular frame of reference. In other words, motion cannot be described without specifying a frame of reference. The laws of physics are the same in all inertial frames of reference, but the description of motion may be different depending on the chosen frame of reference. For example, an object may appear to be stationary in one frame of reference but may be moving in another frame of reference.
To accurately describe and analyze motion, it is necessary to define a specific frame of reference from which the position, velocity, and acceleration of an object can be measured. The choice of frame of reference can greatly affect the measurement and analysis of motion, so it is important to choose the most appropriate frame of reference for the problem at hand.