You are presented with the question "the what is a defense against harmful particles from entering the body" and the following answer choices: 
- lungs
 - It remains dormant
 - A virus
 - immune system
 - exoskeleton
 - pancreas
 - chickenpox
 - liver

Now knowing that abreathing mask is used for keeping harmful particles from entering the respiratory system and another respiratory defense is the immune system, choose the best answer.


 

    immune system     