Answer:
B. In order for oxygen to remain in the blood
Step-by-step explanation:
The hemoglobin is a protein in the blood whose function is to capture the oxygen in the lungs and carry it to the tissues and organs. This protein binds to oxygen but also, to carbon dioxide.
When the plasma in returning to the lungs the carbon dioxide needs to stay low because carbon dioxide has approximately 210 more affinity to hemoglobin than oxygen. This means that a single carbon dioxide molecule binds 210 times harder to the hemoglobin than oxygen. If the carbon dioxide levels are high the hemoglobin will bind to this CO2 instead of binding to the oxygen. If the hemoglobin is not carrying oxygen to the tissues and organs, they will suffocate due to a lack of oxygen and excess of CO2.