Final answer:
The longer the relative stride, the faster the pace. Average velocity can be less than, greater than, or equal to average speed depending on the path taken. Acceleration is the rate of change of velocity, and on a position versus time plot, the slope represents velocity.
Step-by-step explanation:
The question is addressing the relationship between stride length and a certain aspect of motion. The sentence can be completed as: The longer the relative stride, the faster the pace. This is based on the concept that in cases where stride length increases without a decrease in stride frequency, an individual or animal can move more quickly, which is often referred to as the 'pace'.
Now, let's address parts C and D from the provided reference information. If we are comparing average velocity and average speed, the magnitude of average velocity can be either greater than, less than, or equal to average speed, depending on the specifics of the motion. Average speed is defined as the total distance covered divided by the time interval, while average velocity is the total displacement divided by the time interval. Because displacement can be less than (or equal to) the distance if the path is not a straight line, it's possible for the magnitude of average velocity to be less than the average speed.
Regarding the rate of change of velocity, the correct term is acceleration, as indicated in option d of the given choices. Finally, on a position versus time plot, the slope represents velocity, not displacement or acceleration.