Fact 1: Riding a bike does not cause pollution.

Fact 2: Pollution is anything that spoils the environment.

Given the two facts above, answer the question "What does not spoil the environment?" with the following options: 
- Operating a factory
 - Driving a car
 - Riding a bike
 - food and shelter
 - hydrate their cells
 - lowered energy cost
 - Burning a fire
 - peachleaf willow


 

   Riding a bike      