You are presented with the question "Blowing air into what causes air to move inside it?" and the following answer choices: 
- heat
 - solid plastic
 - solid glass
 - solid rock
 - whistle
 - sound
 - a chime
 - waves

Now knowing that blowing air into a whistle causes air to vibrate inside the whistle and when an object moves or vibrates, the air molecules around the object also vibrate, choose the best answer.


 

     whistle    