Fact 1: Muscles can only contract.

Fact 2: Bones work with muscles to perform movement.

Given the two facts above, answer the question "What enables bones to perform movement?" with the following options: 
- contraction
 - Energy
 - sensory neurons
 - looseness
 - Chemical energy
 - Vibrates
 - fur and fat
 - layers of fat


 

 contraction        