You are presented with the question "What causes a bike to move?" and the following answer choices: 
- Coal power
 - energy
 - friction
 - magic
 - mechanical
 - Human power
 - Dog power
 - Energy.

Now knowing that pushing on the pedals of a bike cause that bike to move and well, when riding a bike, human power is used to turn the pedals, choose the best answer.


 

      Human power   