Fact 1: When an animal moves , chemical energy is converted to mechanical energy.

Fact 2: Digestive processes include mechanical, chemical and enzymatic mechanisms.

Given the two facts above, answer the question "what makes it possible for an animal to move?" with the following options: 
- Limbs
 - four limbs
 - digestion
 - stamina
 - motility
 - magnets
 - radiation
 - weather


 

   digestion      