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: chemical weathering causes iron in rock to oxidize, Fact2: Chemical weathering is the chemical disintigration of rocks., Question: what causes iron in rocks to oxidize? (A) a tree falling (B) oxidation reaction (C) exposure to cold (D) chemical disintegration (E) hydrogen and oxygen (F) basic building blocks of life (G) fissures of hot, acidic water (H) flow of electrons
D