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

Fact 2: Breathing Stomach muscles press against the resistance of the diaphragm.

Given the two facts above, answer the question "What is pressed against when mammals breathe?" with the following options: 
- objects that have mass
 - the skin
 - an organism's body
 - an object
 - layers of fat
 - matter vibrating
 - a cuticle
 - stomach muscles


 

        stomach muscles 