A student designs an experiment to test the force of a spring using a spring launcher and four spheres with the same diameter but with different masses. What other piece of equipment would be most useful for this experiment?

a. A graduated cylinder to measure the volume of each sphere before the sphere is launched
b. A beaker to collect the spheres after they are launched
c. A stopwatch to measure how long it takes to load each sphere on the spring
d. A meter stick to measure the height each sphere reaches after the sphere is launched