Which statement accurately describes red blood cells (RBC)?

The statement that accurately describes red blood cells (RBC) is that they primarily carry oxygen and carbon dioxide. Red blood cells are specifically designed to transport oxygen from the lungs to the rest of the body and return carbon dioxide from the body back to the lungs for exhalation. This function is facilitated by hemoglobin, a protein within these cells that binds to oxygen and carbon dioxide efficiently.

Regarding the other statements, while red blood cells play a key role in the body's overall function, their primary function is gas exchange, not directly fighting diseases, which is more characteristic of white blood cells. Additionally, red blood cells have a lifespan of around 120 days, significantly less than a year. They are also not the smallest type of blood cells; that distinction typically belongs to platelets or perhaps some smaller components of the blood. The main role of RBCs in gas transport highlights their essential function in maintaining proper oxygen levels and supporting cellular respiration throughout the body.