Fact 1: Animals can communicate with sounds, chemicals, or visual cues.

Fact 2: Unlike animal communication, properly human communication is abstract and linguistic in nature.

Given the two facts above, answer the question "Which of the following do humans not use to communicate?" with the following options: 
- chemicals.
 - limb amputation
 - emissions
 - sweating
 - smoking pipes
 - dry conditions
 - visible energy
 - heat or cold


 

 chemicals.        