Q: In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
A balloon is filled with Helium, and then is opened and pressed up to someone's mouth to make a voice high, why does it do this? (A) gas fills the new area (B) gas easily is dispersed (C) gas moves around freely (D) gas is lighter than air
A:
A