Answer: Capillaries
Explanation: Blood vessels have the same basic structures used to circulate blood of different composition to and away from the heart to the body. Blood vessels are arteries, veins and capillaries. Arteries carry oxygenated blood from the heart to the body and veins carry deoxygenated blood from the tissues to the heart.
Capillaries are the ones that work with body cells for exchange.They collect nutrients and oxygen from the blood to the cell and also collect carbon dioxide and waste from the cell to the blood which is transported to the vein where it travels via the venous system and goes through the heart, then to the lungs for gaseous exchange.
Therefore the enswer is, capillaries.