What characteristic distinguishes viruses from bacteria?

The characteristic that distinguishes viruses from bacteria is that viruses cannot reproduce on their own. Unlike bacteria, which are single-celled organisms capable of independent growth and reproduction, viruses require the cellular machinery of a host organism to replicate and increase in number. When a virus infects a host cell, it hijacks the host's cellular machinery to produce copies of itself. This fundamental difference is key in understanding how viruses operate compared to bacteria.

The other options do not accurately convey this important distinction. Viruses are actually much smaller than bacteria, not larger. Additionally, while some viruses can thrive in extreme conditions, bacteria generally have a broader range of survival capabilities in harsh environments. Understanding these differences is crucial in fields like microbiology and healthcare, particularly in infection control and disease management.