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: Hydrogen bonds cause water to expand when it freezes., Fact2: Water is made up of H2O molecules., Question: What bonds cause H2O to expand when freezing? (A) Covalent (B) Hydrogen (C) Metallic (D) an ion (E) Heat energy (F) Ionic (G) heat (H) an anion
Output:
B