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: fluoride decreases tooth decay, Fact2: Fluorides Fluorides are the salts of hydrofluoric acid., Question: The salts of hydrofluoric acid do what to tooth decay? (A) heating (B) amebiasis (C) swelling nodes (D) Type O (E) secreting (F) decrease it (G) precipitation (H) hard tissue
F