You are presented with the quiz "Doing what to food can extend shelf life by removing microorganisms?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "killing microorganisms in food can be used to extend the shelf life of that food" and "irradiation kills microorganisms that spoil food". 

So, what's the best answer to the question?


 

       irradiating    