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.
Because of the food chain link between clovers, deers, and wolves, when the population of clovers decrease, deers will starve and their population will decrease. Same thing happens to the wolves, because their food source is the deer, unless they hunt other prey, they will also starve.
