Answer
C, A, B.
Work Step by Step
The cups in C self-correct as they roll, making them the most stable. If they deviate to, say, the right, the new larger effective diameter of the wheel on the right will result in a larger tangential speed, bringing the cups back toward the center. This is discussed on page 135.
System A is neutral.
The cups in B are the least stable. If they deviate to, say, the right, the new smaller effective diameter of the wheel on the right will result in a smaller tangential speed on that side, throwing the cups even more off-center.
