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: thirst is used to make an animal realize that it needs to replenish its bodily water by the body, Fact2: Water hydrates the cells., Question: Thirst is used to make animals realize they need to what? (A) remove their cells (B) filter their beverages (C) recovery time from fatigue (D) reusing things (E) moisturize their eyes (F) hydrate their cells (G) Converting waste. (H) they body they live in
F