What best describes viruses?

Viruses are best described as tiny packets of RNA or DNA surrounded by a protein or lipid coating. This definition is accurate because viruses are acellular entities, meaning they are not made up of cells and cannot carry out metabolic processes on their own. They consist of either genetic material (DNA or RNA) encased in a protective coating, which can be made of proteins or lipids. This structure enables them to invade host cells, where they can replicate and produce new virus particles.

In contrast, other descriptions are inaccurate. Living cells that reproduce independently refer to organisms, such as bacteria, that can thrive on their own without the need for a host. Multi-cellular organisms that can grow in environments describe complex life forms, which is not applicable to viruses. Lastly, encapsulating bacteria as entities that can reproduce independently does not align with the nature of viruses, which lack independent reproductive capabilities. Instead, viruses must hijack the cellular machinery of a host organism to replicate.