Final answer:
A stationary building on the ground is a suitable reference point to show motion when riding an airplane headed west, providing a clear representation of movement compared to a non-moving background.
Step-by-step explanation:
When you are riding on an airplane that is headed west, a good reference point that could show your motion is a stationary building on the ground. This is because a stationary reference frame allows you to observe the motion relative to a non-moving background, making it apparent that the airplane is in motion. For example, looking at a building as the plane passes by would clearly show that the airplane is moving west, similar to how the classroom walls can serve as a stationary reference to observe motion in a classroom scenario.