You are presented with the question "overcoming the energy barrier starts a what" and the following answer choices: 
- chemical reaction
 - contraction
 - Movement of an air mass
 - expansion
 - metabolic reaction
 - energy storage
 - increased body strength
 - oxidation reaction

Now knowing that all chemical reactions require activation energy to get started and activation energy is required to overcome the energy barrier, choose the best answer.


 

 chemical reaction        