Answer:
Environment.
Step-by-step explanation:
The respiratory system interacts with the environment by contracting and expanding the diaphragm and chest in order to do breathing. When the muscles in the diaphragm contracts and the expansion of chest occurs, takes the air inside the body that is present in the outside environment for inhalation of oxygen while on the other hand, when the diaphragm expands and chest contract, the air inside the body is removed with the removal of carbondioxide gas.