What Is The Function Of Red Blood Cells?

Ok, first of all... Hemoglobin is a protein in the red blood cells (erythrocytes) and it's what makes the blood cells red.

the principal function of red blood cells is delivering oxygen to the body tissues. They take up oxygen in the lungs and release it while squeezing through the body's capillaries.

Carries oxygen through the blood stream

Carry oxygen to tissues and organs

To carry oxegen to the tissues

I believe it is..hemoglobin ( which is oxygen)
if it's not hemoglobin then it would be for immunity, but I'm pretty sure that's for white blood cells

They carry oxygen to the cells of the body and carry carbon dioxide to the lungs so it can be exhaled.