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

Fact 2: Sound vibrations have different frequencies.

Given the two facts above, answer the question "What  can be used for communication by animals?" with the following options: 
- electricity
 - energy
 - Telephones.
 - Vibrations.
 - Stuffed animals.
 - messengers
 - courtship
 - Cellular communication.


 

    Vibrations.     