Answer:
The word that best complete the sentence is VIRUSES.
Explanation:
There are different types of microorganisms, one of them is virus. Viruses are different from other forms of microbes because they need living cells to become active; outside living cells they are inactive and did not exhibit any of the features of living things.
Viruses only grow and multiply when they are withing the cells of another living thing; they do not have the capacity to survive and reproduce outside a living host.
