Viruses need to be inside a living thing (of course the living thing has to have the right temperature which most living things do) . When they're inside a living thing they start injecting the host's cells with its DNA in order to make more copies of itself which allows the virus to spread. So basically viruses need to be inside something living.
I think its option b, may carry out nitrogen fixation.
<span>Well active transport absolutely moves substances against their concentration gradient (answer C), although I dislike how the other answers could probably be argued for. This seems to be a case of pick the "best" answer</span>
