It should be carbohydrates
its the circulatory system
C. Is the answer for sure
<span><span>The blood cells containing hemoglobin, that transports oxygen (O2) to the body tissues of vertebrates, are called red blood cells.</span> Red blood cells (RBCs), are also referred to as red cells, red blood corpuscles, haematids, erythroid cells or erythrocytes<span>, (from Greek erythros for "red" and kytos for "hollow vessel"..RBCs take up oxygen in the lungs and release it into tissues while squeezing through the body's capillaries.</span></span>
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