Fact 1: Eyes are used for seeing by animals by sensing light.

Fact 2: Visible and invisible light is energy in the form of electromagnetic waves.

Given the two facts above, answer the question "Eyes are used by animals for seeing by sensing what?" with the following options: 
- focusing a lens
 - an electron microscope
 - objects that have mass
 - chemical messengers
 - basic building blocks of life
 - electromagnetic waves
 - matter vibrating
 - rain or sun shine


 

      electromagnetic waves   