D is the answer to this question hope it helps
If a human’s red blood cells will lack sufficient amount of
hemoglobin, he or she would have also a low amount of oxygen.
Hemoglobin is what makes the red blood cells red in color,
aside from the abnormal color, the red blood cells also make up of oxygen. It can also be with iron since iron is bind
to hemoglobin all the way to the lungs.
