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

Fact 2: Animals use sound in sophisticated ways.

Given the two facts above, answer the question "animal what is sophisticated" with the following options: 
- exoskeleton
 - four limbs
 - communication
 - nervous system
 - hormones
 - in the frog family
 - proteins
 - circulatory systems


 

   communication      