What is the primary function of red blood cells in the human body?

The primary function of red blood cells, or erythrocytes, is to transport oxygen throughout the body. Hemoglobin, the protein contained within red blood cells, binds to oxygen in the lungs and carries it to tissues and organs where it is needed for cellular respiration and energy production. This process is essential for maintaining the metabolic functions of cells and ensuring that the body operates effectively.

In addition to their role in oxygen transport, red blood cells also help transport a small amount of carbon dioxide back to the lungs for exhalation, playing a crucial part in gas exchange. While other components of blood, such as white blood cells, are responsible for fighting infections, and platelets contribute to blood clotting, red blood cells are specialized primarily for delivering oxygen, making option B the correct answer.