Answer:
Viruses cannot reproduce on their own, but inject their DNA into living cells in order to make copies of themselves.
Explanation:
A virus cannot reproduce itself outside the host because it lacks the complicated machinery that a [host] cell possesses.
Systematic separation of the circulation of the blood. The right side of the heart receives oxygen-poor blood from your body and pumps it to the lungs. The lungs oxygenate the blood which returns to the heart and is pumped to the rest of the body by the left side of the heart. After which the blood returns to the right side, completing the cycle of circulation.
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