I think it’s C but I’m not fully sure so wait for others just to make sure
Answer:
Everything in Earth's system such as water, land, air, and or living things.
Explanation:
All those things are called "Spheres" or specifically =
1- Hydrosphere (water)
2- Lithosphere (land)
3- Biosphere (living things)
4- atmosphere (air)
Gas exchange is the delivery of oxygen from the lungs to the blood stream, and gets rid of carbon dioxide from the blood. It occurs in the lungs between the alveoli and a group of capillaries.
