Answer the following question given this paragraph: 

Did you ever wonder how a microwave works? It directs invisible waves of radiation toward the food placed inside of it. The radiation transfers energy to the food, causing it to get warmer. The radiation is in the form of microwaves, which are a type of electromagnetic waves.


Q: What type of invisible waves are used in microwaves?

 Choices:

- convection

- electric

- thermal

- radiation

A:
radiation
