What do erythrocytes primarily transport in the human body?

Erythrocytes, or red blood cells, primarily transport oxygen from the lungs to the tissues of the body. This function is facilitated by hemoglobin, a protein within the erythrocytes that binds to oxygen molecules in the lungs where oxygen concentration is high. As the erythrocytes circulate through the bloodstream, they deliver this oxygen to the body's tissues, where the oxygen is used for cellular respiration and energy production.

While erythrocytes do play a role in the transportation of carbon dioxide back to the lungs for exhalation, their primary role is the conveyance of oxygen, which is essential for sustaining cellular functions throughout the body. Nutrients and hormones, on the other hand, are primarily transported by plasma and specific transport proteins in various systems rather than by erythrocytes themselves. Therefore, the correct answer highlights the vital role of erythrocytes in oxygen delivery, underscoring their importance in maintaining the physiological processes necessary for life.