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

Fact 2: First, overcoming inertia to move forward is difficult.

Given the two facts above, answer the question "What must be overcome when pushing on bike pedals?" with the following options: 
- hormones
 - Pollution
 - heat
 - activity
 - animation
 - inertia
 - friction
 - energy


 

      inertia   