Cells need oxygen to make energy. oxygen-rich blood is transported to tissues. when the oxygen is dropped off, it needs to move through structures that are small and thin. which vessels allow for oxygen movement into the tissues? arteries veins heart capillaries

Capillaries

Explanation: There are two kinds of vessels which carry the blood throughout the body. These are veins and arteries. Now apart from these two, there is a third type which is called as capillaries, which are the connecting vessels between arteries and veins. These are relatively thinner and allow exchange of gases between tissues and the blood. Therefore, arteries and veins are incorrect options.

Heart is the pumping organ, and its function is to pump the blood to every cell of the body, so this can't be correct option.