All but one factor contributes to natural selection. that factor is a) mutation. b) random mating. c) genetic drift. d) environmental factors.

The answer is b or d but I really think its b 

B. Mutation i think

When the ball is rising up, it gains kinetic energy. when the ball reaches the very top, it will have all potential energy, until it falls back down and gains it kinetic energy. finally when you catch the ball or it falls back down, it would have gained its potential energy back.