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: blowing air into a whistle causes air to vibrate inside the whistle, Fact2: Air, too, contains oxygen., Question: If you blow oxygen inside of a whistle, what will vibrate inside of the whistle? (A) an object (B) friction (C) energy (D) waves (E) heat (F) oxygen (G) a chime (H) sound
Output:
F