Fact 1: Skin is used for protecting the body from harmful substances.

Fact 2: Skin is a protective organ.

Given the two facts above, answer the question "What does skin help keep out?" with the following options: 
- medicine
 - sun's heat
 - heat
 - hurtful words
 - a pathogens
 - parasites
 - harmful substances
 - Echinoderm.


 

       harmful substances  