Fact 1: Irradiating food can be used to kill existing microorganisms in the food.

Fact 2: Irradiation causes chemical changes.

Given the two facts above, answer the question "what can be used to kill existing microorganisms in food?" with the following options: 
- chemical changes
 - Dehydration
 - deoxyribonucleic acid
 - bacteria
 - an electron microscope
 - hydration
 - electromagnetic energy
 - single-celled organisms


 

 chemical changes        