You are presented with the quiz "What can keep mold from entering the respiratory system?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "abreathing mask is used for keeping harmful particles from entering the respiratory system" and "when mold grows in the house, it can emit particles that travel through the air". 

So, what's the best answer to the question?


 

     a breathing mask      