A student conducts an experiment to determine the speed of a toy car at the bottom of a ramp after it is released from different heights on the ramp. The student makes one measurement for each height. What is one way that the student could improve the experiment?

(A) Use a different timer for height.
(B) Use a different ramp for each height.
(C) Perform one trial for each measurement but use a different car for each height.
(D) Perform multiple trials for each release height instead of just one.