When driving downhill, your vehicle will accelerate and start moving fast, due to
a. kinetic energy
b. gravity
c. the amount of pressure you put on the accelerator pedal
d. wet pavement

I think the correct answer from the list of choices above is option B. When driving downhill, your vehicle will accelerate and start moving fast, due to gravity. The gravity will add more force to the vehicle allowing it to move faster than in a vertical position.