it the reader understand new concepts.
your answer would be a verb. because they are "doing something"
answer: b (host)
viruses use the cells of living organisms to reproduce. the cell which is used by virus is called as "host cell". it is a living cell in which virus multiplies, example bacteria, plant or an animal cell.
in this, the virus is a parasite, which uses host cell for its benefit (reproduction) by using the cell machinary of host cell.