What is the stage called where the viral nucleic acid is integrated into the host cell's nucleic acid?

The correct stage where the viral nucleic acid is integrated into the host cell's nucleic acid is referred to as the synthesis stage. During this phase, after the virus has entered the host cell, the viral genome is incorporated into the host's genetic material, allowing the viral genes to be expressed and replicated alongside the host's DNA.

Synthesis is a critical part of the viral replication cycle, particularly for viruses with a lysogenic life cycle, such as certain retroviruses. The integration allows the virus to leverage the host's cellular machinery for replication and expression of viral proteins, ultimately leading to the assembly of new virions.

In contrast, the assembly stage is where newly synthesized viral components are put together to form complete virions, the release stage involves the exit of new virions from the host cell, and the entry stage encompasses the virus's entry into the host cell. Understanding these stages helps to clarify the lifecycle of viruses and how they interact with host cells, which is essential for developing antiviral strategies.