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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Is the problem true of false
<span>They have very stable outer electron shells</span>
I'm not sure what the options are for an answer but based on what I remember from my ENTO class, it would be secondary myiasis.