Fact 1: Killing microorganisms in food can be used to extend the shelf life of that food.

Fact 2: Irradiation kills microorganisms that spoil food.

Given the two facts above, answer the question "Doing what to food can extend shelf life by removing microorganisms?" with the following options: 
- warming
 - Dehydration
 - cooling
 - Cooking
 - bacteria
 - burning
 - irradiating
 - hydration


 

       irradiating  