Fact 1: Sound can be used for communication by animals.

Fact 2: Orangutans have a vocal repertoire of about 13 sounds.

Given the two facts above, answer the question "Orangutans can communicate by doing what?" with the following options: 
- mental telepathy
 - Infomercials
 - contracting
 - singing opera
 - focusing a lens
 - vocalizing
 - adding heat
 - unidirectional


 

      vocalizing   