Final answer:
The rate at which the tip of a shadow moves is proportional to the sun's angle. As the sun's angle changes, the length of the shadow will change, resulting in a varying rate of movement.
Step-by-step explanation:
The rate at which the tip of a shadow moves is proportional to the sun's angle (B). As the sun's angle changes, the length of the shadow will change. When the sun is directly overhead, the shadow will be shortest and the rate of change will be the highest. As the sun sets, the angle decreases and the shadow grows longer, resulting in a slower rate of change.