What role do red blood cells play in the body?

Red blood cells, or erythrocytes, primarily function to transport oxygen from the lungs to the body's tissues and return carbon dioxide from the tissues back to the lungs. This role is crucial for maintaining the body's respiratory function and ensuring that cells receive the oxygen needed for energy production and metabolic processes. The protein hemoglobin, found within red blood cells, binds to oxygen, allowing for this effective transport.

In contrast, the other options relate to different types of blood cells or bodily functions. For instance, white blood cells are the primary defenders against disease and infection, while platelets are involved in the blood clotting process. While elements of the immune system do support immune function, it is the red blood cells that are specifically responsible for the transport of gases, making their role distinct and vital to overall health and survival.