Which of the following acellular infectious agents can reproduce only when inside a host cell?

• A. Viroids
• B. Viruses
• C. All of the above
• D. Prions

Answer: (B)

Verified step by step guidance

1. Understand the nature of each acellular infectious agent listed: viruses, viroids, and prions.
2. Recall that viruses consist of genetic material (DNA or RNA) enclosed in a protein coat and require a host cell's machinery to reproduce because they lack the cellular components necessary for independent replication.
3. Recognize that viroids are small, circular RNA molecules that infect plants and can replicate only within host cells, but they do not produce proteins or form viral particles like viruses.
4. Know that prions are misfolded proteins that cause disease by inducing misfolding in normal proteins; they do not contain nucleic acids and do not reproduce in the traditional sense, but propagate by protein conformational change.
5. Conclude that among the options, viruses are the acellular infectious agents that reproduce only inside host cells by hijacking the host's replication machinery.