What do viruses do once they invade a living cell of a host?

• A. They replicate using the host's cellular machinery.
• B. They produce energy independently of the host cell.
• C. They become dormant and do not affect the host cell.
• D. They immediately kill the host cell.

Answer: (A)

Verified step by step guidance

1. Understand that viruses are not capable of independent reproduction and rely on a host cell's machinery to replicate.
2. Once a virus invades a host cell, it injects its genetic material into the host.
3. The viral genetic material hijacks the host cell's machinery, directing it to produce viral components instead of the host's normal products.
4. These components are assembled into new virus particles within the host cell.
5. Eventually, the host cell releases the new viruses, often resulting in the cell's death, allowing the viruses to infect additional cells.