What is the primary function of red blood cells?

The primary function of red blood cells, also known as erythrocytes, is to carry oxygen from the lungs to the rest of the body. This is accomplished through a protein called hemoglobin, which binds to oxygen molecules in the lungs and releases them in tissues where oxygen is needed. By delivering oxygen, red blood cells play a vital role in supporting cellular metabolism and overall bodily function.

While the other options describe important processes that involve different types of cells in the body, they do not accurately reflect the main role of red blood cells. White blood cells are responsible for fighting infections, as they are part of the immune system. The removal of waste from the body is primarily a function of organs like the kidneys, rather than red blood cells. Digestion is aided by enzymes and cells in the digestive system, not by red blood cells. Thus, the focus on oxygen transport solidifies why the function of red blood cells is essential for life.