Which of the following are key characteristics of viruses?

The characteristics attributed to viruses are best captured by the description of being acellular, consisting of genetic material, and requiring a host cell for replication. Viruses are not composed of cells and do not possess the cellular machinery to reproduce independently. Instead, they rely on the metabolic processes of a host organism to replicate and propagate.

The acellular nature of viruses means they do not have typical cellular structures such as cell walls or membranes found in living organisms. Their genetic material, which can be either DNA or RNA, is enclosed in a protein coat called a capsid, and sometimes they also have an additional lipid envelope. The requirement for a host cell is critical, as viruses must hijack the host's cellular machinery to produce their proteins and replicate their nucleic acids.

Other options incorrectly describe viruses. For instance, the idea of being multicellular, containing cell walls, and reproducing independently does not reflect the fundamental nature of viruses, which are neither multicellular nor capable of independent reproduction. Additionally, describing viruses as unicellular, having a nucleus, and producing energy misrepresents them; viruses lack cellular structures entirely and do not generate energy through metabolism. Finally, the notion that viruses are cellular and possess both DNA and RNA and can replicate on their own