Fact 1: Blowing air into a whistle causes air to vibrate inside the whistle. Fact 2: Sounds are caused by vibrations in the air. Given the two facts above, blowing what into a whistle causes sound?

Options: i. a lack of noise ii. CFCs iii. CO 2 iv. a lack of sound v. wind vi. air vii. gas viii. no noise
Answer:
vi.