Fact 1: Abreathing mask is used for keeping harmful particles from entering the respiratory system.

Fact 2: Oxygen enters the respiratory system through the mouth and the nose.

Given the two facts above, answer the question "Breathing masks are used to keep harmful particles from entering the mouth and the what?" with the following options: 
- body
 - eyes
 - air
 - skin
 - gullet
 - nose
 - ears
 - lungs


 

      nose   