You are presented with the question "Orangutans can communicate by doing what?" and the following answer choices: 
- mental telepathy
 - Infomercials
 - contracting
 - singing opera
 - focusing a lens
 - vocalizing
 - adding heat
 - unidirectional

Now knowing that sound can be used for communication by animals and orangutans have a vocal repertoire of about 13 sounds, choose the best answer.


 

      vocalizing   