Which of the following statements about viruses is true?

• A. They reproduce inside host cells.
• B. They reproduce outside cells.
• C. They are not contagious.
• D. They only affect plants.

Answer: (A)

Viruses reproduce inside host cells because they lack the full cellular machinery needed to copy their genome and build viral components on their own. A virus is essentially genetic material enclosed in a protein coat that must hijack a living cell to replicate. It attaches to a cell, injects its genome, and then uses the cell’s machinery—ribosomes, enzymes, and energy—to produce viral proteins and copy the viral genome. New virus particles are assembled inside the cell and released, often damaging or killing the host cell in the process. Because of this dependency on living cells, statements saying viruses reproduce outside cells are incorrect, and they aren’t limited to plants since viruses can infect a wide range of hosts, including animals and bacteria. They can be contagious, but spreading isn’t the defining factor of how they replicate.