An engineering student is gathering data on the motion of a model car traveling down a ramp. If energy is conserved, the potential energy of the car at the top of the ramp should equal the kinetic energy at the bottom of the ramp. After the first trail, the student calculates that the kinetic energy at the bottom of the ramp is less than the potential energy at the top of the ramp. Which of the following best explains the difference?​ A. the student did not include the effect of friction in his calculation
B. the student accidentally accelerated the car at the top of the ramp
C. the measure height of the ramp was less than the actual height
D. The car gained a small amount of mass as it moved down the ramp