What structure is most likely found in both viruses and cells?

The correct answer is - Proteins

Explanation:

Protein is the structure that is found in both virus and cells. The capsid of a virus is made up of many structural subunits of proteins known as protomers. This capsid makes the outer covering of viruses inside which the genetic material of the virus is enclosed. The genetic material can be DNA or RNA.

In prokaryotic and eukaryotic cells the proteins are produced by the translation process. These proteins are essential for cell communication, enzyme synthesis, membrane integration, metabolism, etc. Therefore protein is the structure that is most likely to be found in both viruses and cells.