The best and most correct answer among the choices provided by your question is the first choice or letter A. <span>A biological agent that cannot reproduce on its own is a VIRUS.
</span>A virus<span> is a small infectious agent that replicates only inside the living cells of other organisms.
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These are sources of very good cavier. The beluga is actually a whale, while the osetra is a sturgeon. The sevruga is also a sturgeon.