Most viruses ... can use host machinery to produce more of themselves are persistent and innocuous within host cells switch between pathogenic and non-pathogenic modes of existence kill the cell they infect are rarely found in the natural world.

Answer: Most viruses can use host machinery to produce more of themselves

Explanation:

Since viruses carry out no metabolism themselves, they rely solely on the living cells of the host (organism they infect) to replicate and spread from cell to cell.

Thus, viruses do not kill the cells they infect since they need them, and use them to replicate more offsprings