Fact 1: Mammals breathe with the help of a diaphragm.

Fact 2: When the diaphragm moves down, air is pulled into the lungs.

Given the two facts above, answer the question "What breathes by pulling air into the lungs?" with the following options: 
- humans
 - animals
 - bears
 - sponges
 - mammals
 - bacteria
 - goats
 - oxygen


 

     mammals    