Eons: Hadean, Archean, Proterozoic
All of the above is the answer.
The flow of oxygen is simply summarized as entering the body through the lungs and being absorbed into the blood. From there, the oxygenated blood is carried to the heart and then pumped all over the body. From there, the oxygen is absorbed by cells that need it for respiration.
Carbon dioxide is generated via respiration of glucose in muscle and body cells. It then passes into the blood and is carried out to the lungs, where it diffuses out and is breathed out.
Blood follows a double circulation pattern, where deoxygenated is pumped to the lungs from the heart then goes back to the heart to be pumped into the rest of the body.
