Fact 1: Pushing on the pedals of a bike cause that bike to move.

Fact 2: Force is a push or a pull.

Given the two facts above, answer the question "What on the pedals of a bike cause that bike to move?" with the following options: 
- force
 - heat
 - nothing
 - a lack of energy
 - zero energy
 - muscles
 - speed
 - motion


 

 force        