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, answer the question "What does blowing into a whistle do?" with the following options: 
- makes a sight
 - makes sound
 - causes disruption
 - duplicate itself
 - unidirectional
 - decrease stamina
 - makes hearing
 - to move people


 

  makes sound       