Possible answers:
(I) sweating.
(II) hormones.
(III) quadriceps.
(IV) smooth surfaces.
(V) electrically.
(VI) friction.
(VII) speed.
(VIII) lack of friction.
Q: Fact 1: Friction causes an object to lose energy. Fact 2: With less energy, the electron slows down. Given the two facts above, what causes an object to slow down?
A:
(VI)