Which statement correctly describes viruses?

• A. They replicate independently without a host
• B. They are cellular organisms with a nucleus
• C. They are acellular obligate parasites requiring a host cell to replicate
• D. They are larger than bacteria

Answer: (C)

Viruses are not independent, cellular organisms. They lack cellular structures and metabolic systems, so they cannot carry out replication on their own. Instead, they must hijack a living cell’s machinery—enzymes, ribosomes, and energy pathways—to replicate their genetic material and assemble new virus particles. This makes them acellular obligate parasites: they require a host cell to reproduce at all.

That’s why the statement that viruses are acellular obligate parasites requiring a host cell to replicate is the best description. The other ideas don’t fit: viruses do not replicate without a host, they are not cellular organisms with a nucleus, and while many viruses are smaller than bacteria (with a few exceptions), the general point is that viruses are much smaller and fundamentally different from bacterial cells.