8. Arteries carry oxygenated blood from the heart to the rest of the body, while veins carry deoxygenated blood from the body, back to the heart. Arteries are thick and muscular, while veins aren't as thick, and they have valves.
Answer:
they all have cells
Explanation:
each living thing has cells that help them survive and help their body work well.
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A flatworm does not have a body cavity.