Given the task definition and input, reply with output. 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: irradiating food can be used to kill existing microorganisms in the food, Fact2: Irradiation causes chemical changes., Question: what can be used to kill existing microorganisms in food? (A) chemical changes (B) Dehydration (C) deoxyribonucleic acid (D) bacteria (E) an electron microscope (F) hydration (G) electromagnetic energy (H) single-celled organisms
A