A(n) _______ is a blood vessel that carries blood away from the heart. A(n) _______ is a blood vessel that carries blood to the heart.

Answer: A. artery, vein

The correct answer is A. artery, vein.
An artery carries oxygen-rich blood away from the heart to the rest of the body, while a vein carries oxygen-poor blood back to the heart. This rule has only one exception: the pulmonary artery and vein, which handle blood traveling to and from the lungs. Arteries have thick, elastic walls to handle high pressure, whereas veins have valves to prevent blood from flowing backward.

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