Which acellular infectious agent is described as a tiny, nonliving particle that invades and then reproduces inside a living cell?

• A. Bacterium
• B. Virus
• C. Prion
• D. Viroid

Answer: (B)

Verified step by step guidance

1. Understand the definition of an acellular infectious agent: it is a particle that lacks cellular structure and cannot carry out metabolic processes on its own.
2. Recall that bacteria are cellular organisms, so they do not fit the description of acellular infectious agents.
3. Consider prions, which are infectious proteins but do not contain nucleic acids and do not reproduce inside cells in the traditional sense.
4. Consider viroids, which are small infectious RNA molecules that infect plants but are not considered particles that invade cells like viruses.
5. Identify viruses as tiny, nonliving particles composed of nucleic acid (DNA or RNA) enclosed in a protein coat that invade living cells and use the host's machinery to reproduce.