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

Fact 2: Well, when riding a bike, human power is used to turn the pedals.

Given the two facts above, answer the question "What causes a bike to move?" with the following options: 
- Coal power
 - energy
 - friction
 - magic
 - mechanical
 - Human power
 - Dog power
 - Energy.


 

      Human power   