What characteristic distinguishes bacteria from viruses?

Bacteria are generally larger than viruses, which is a key characteristic that distinguishes the two. Bacteria are single-celled organisms that can exist independently and have a cellular structure, including a cell wall, membrane, and ribosomes. In contrast, viruses are much smaller, consisting of genetic material encased in a protein coat, and they lack the cellular machinery necessary for independent life.

In relation to the other choices, while it is true that bacteria can replicate on their own, viruses cannot; however, this statement does not provide a distinguishing feature, and the option implying that bacteria cause no harm overlooks their potential pathogenic effects. Lastly, the assertion that bacteria require host cells to multiply is specifically true for viruses, not bacteria, which can reproduce independently in numerous environments. Therefore, the correct answer highlights the physical size difference that sets bacteria apart from viruses.