What is the difference between a virus and a bacteria?

Viruses and bacteria are fundamentally different in their structure and replication methods. The correct choice highlights that viruses cannot reproduce on their own; they require a host cell to replicate. This is due to the fact that viruses lack the cellular machinery necessary for metabolism and reproduction. Instead, they invade host cells and hijack the host's cellular processes to produce more virus particles.

In contrast, bacteria are single-celled organisms that can live and reproduce independently in various environments, such as in soil, water, and within the bodies of living organisms. They possess the necessary cellular components for metabolism and replication, which enables them to thrive outside of a host.

This difference in reproduction and independence is critical when considering how infections are treated, as it influences the types of medications used. Antibiotics target bacteria specifically and are ineffective against viruses, reinforcing the importance of understanding the distinctions between these two types of microorganisms.