Which statement about red blood cell lifespan is correct?

• A. Bi-concave discs (high carrying capacity, flexible for small spaces)
• B. Carry O2 and Dioxides
• C. No nucleus; no protein production
• D. Live for 120 days

Answer: (D)

Red blood cells have a finite lifespan because they are specialized for gas transport and lack the machinery to repair damage. In mammals, mature RBCs have no nucleus and no mitochondria, so they cannot synthesize new proteins or repair membranes. As they circulate, their membranes wear out and they accumulate oxidative damage, leading to their removal by the spleen and liver. To keep oxygen delivery consistent, new RBCs are continually produced in the bone marrow under erythropoietin control. This turnover means a typical circulating lifespan of about 120 days in humans and many mammals, so the statement that they live for roughly 120 days is correct. The other descriptions relate to shape, function, or cellular composition, which are true but address different aspects rather than lifespan.