How does a virus replicate itself inside a host?

A virus replicates itself inside a host by entering living cells, then utilizing the cellular mechanisms of the host to produce copies of itself. When a virus infects a host cell, it injects its genetic material into the cell. This genetic material can be DNA or RNA, depending on the type of virus. Once inside the host cell, the virus hijacks the host’s cellular machinery—such as ribosomes and enzymes—to replicate its genetic material and produce viral proteins. These newly synthesized components are then assembled into new virus particles that can exit the host cell to infect additional cells.

The process fundamentally relies on the virus gaining entry into the living cell, which makes the chosen answer the correct one. Although viruses do not possess their own cellular structures or machinery, their successful replication is entirely dependent on their ability to infiltrate living cells and manipulate the host’s systems.