In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").

Fact1: eyes are used for seeing by animals by sensing light, Fact2: Visible and invisible light is energy in the form of electromagnetic waves., Question: Eyes are used by animals for seeing by sensing what? (A) focusing a lens (B) an electron microscope (C) objects that have mass (D) chemical messengers (E) basic building blocks of life (F) electromagnetic waves (G) matter vibrating (H) rain or sun shine
F