Definition: 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").
Input: Fact1: chemical weathering causes iron in rock to oxidize, Fact2: Rust colored residues are due to oxidized iron., Question: What causes rust? (A) a pathogens (B) Roundworms (C) flow of electrons (D) dust (E) thunder (F) an amoebae (G) chemical weathering (H) skin
Output:
G