Answer:
Personally, i think this model is wrong because the arrows point that carbon dioxide enters the lungs and leaves as oxygen which is totally the opposite, but he or she has showed that the oxygen breathed in is used in the oxygenation of the blood. I may be wrong but it doesn't seem right if you think about it. But if you look really hard at it, the oxygenated blood changes it to carbon, and then carries it back to the lungs to be inhaled.
Explanation:
