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: Cells cannot survive without oxygen., Fact2: And oxygen, O2, is the molecule to do it., Question: What is something cells cannot survive without? (A) gas (B) Air (C) O2 (D) CO2 (E) Ca (F) O3 (G) Fe (H) He
Output:
C