Average life span of human RBC is

The correct option is 120 days.

Red Blood Cells (RBCs), also known as erythrocytes, are the most common type of blood cell in humans. Their primary function is to transport oxygen from the lungs to the rest of the body's tissues using a specialized protein called hemoglobin.
Unlike most other cells in the body, mature human red blood cells do not have a nucleus or organelles. This structural adaptation allows more space for hemoglobin to carry oxygen efficiently, but it also means that the cells cannot replicate, repair damage, or synthesize new proteins.

As a result, RBCs have a limited lifespan. Over time, their cell membranes become increasingly fragile and worn out from squeezing through tight capillary networks. On average, human red blood cells circulate in the bloodstream for approximately 120 days before they are targeted for destruction.
Once they reach the end of their lifespan, old or damaged RBCs are recognized and broken down by macrophages in the spleen, liver, and bone marrow through a process called phagocytosis. The components of the broken-down cells, such as iron, are then recycled to form new red blood cells in the bone marrow.