Fact 1: All chemical reactions require activation energy to get started.

Fact 2: Chemical changes are a result of chemical reactions.

Given the two facts above, answer the question "What do ALL chemical changes require to occur?" with the following options: 
- during the day
 - heating liquids
 - Activation energy
 - wavelengths and photons
 - Burning fuel and air
 - kinetic energy
 - electromagnetic energy
 - direct energy


 

   Activation energy      