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").
Q: Fact1: Hydrogen bonds cause water to expand when it freezes., Fact2: Water is everywhere H20., Question: What causes H20 to expand when frozen? (A) evaporation (B) vaporization (C) hydrogen bonds (D) helium bonds (E) mysterious forces (F) nitrogen bonds (G) Physical weathering (H) precipitation
A:
C