Test 5, Section 4, Question 20. How do you get to the answer?

Get this by process of elimination.

A) Eliminate this because the question says the wheel is rolling at a constant rate (i.e., speed), so a graph of its speed would be a horizontal line.

B) Eliminate this because the question says the wheel is rolling at a constant rate along a straight, level path. Therefore, its distance from its starting point as a function of time would also be a straight line with a positive slope—the graph would get higher and higher the longer the wheel rolled.

C) Eliminate this because the mark on the rim will always be the same distance (the radius) from the center of the wheel.

D) By process of elimination this must be right. You might also recognize the similarities of the setup of this question to a model you might have seen in trigonometry when you were introduced to the sine curve: