Question

What role do red blood cells play in the human body?

They protect against injury.
They protect against disease-carrying microorganisms.
They transport oxygen throughout the body.
They aid in blood clotting.

Answer 1

They transport oxygen throughout the body — red blood cells (erythrocytes) carry oxygen bound to hemoglobin (and help transport some CO2). The other functions are done by platelets (clotting) and white blood cells (immune defense).