You are presented with the question "What does skin help keep out?" and the following answer choices: 
- medicine
 - sun's heat
 - heat
 - hurtful words
 - a pathogens
 - parasites
 - harmful substances
 - Echinoderm.

Now knowing that skin is used for protecting the body from harmful substances and skin is a protective organ, choose the best answer.


 

       harmful substances  