Final answer:
The potential energy for a mass on a spring is proportional to the square of the displacement.
Step-by-step explanation:
The potential energy for a mass on a spring is proportional to the square of the displacement of the mass from its equilibrium position.
This can be seen in the formula for the potential energy stored in a spring, which is given by U = (1/2)kx², where U is the potential energy, k is the spring constant, and x is the displacement. The answer to the student's question is d. Displacement.