Help please Veins have to ensure that blood under low pressure can return to the heart.
The circuit of circulation that goes from the heart to the body cells and back to the heart is called circulation.
he oxygenated and deoxygenated blood are kept separate in the mammalian heart by the .

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Explanation:

i think that it is plants

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called