Viruses lack cellular structure and nuclei

Steps:

• Recall that viruses are acellular entities without true cells or nuclei, distinguishing them from bacteria, fungi, and protozoa.
• Examine each option for the absence of cells and nuclei, as these are defining viral traits.
• Note that viruses do not produce spores, unlike some cellular microbes.
• Identify the option matching all viral characteristics: no cells, no nuclei, no spores.

Why C is correct:

• Viruses are non-cellular (no cells or nuclei) and do not reproduce via spores, per the definition of viruses as obligate intracellular parasites with nucleic acid in a protein coat.

Why the others are wrong:

• A describes eukaryotic cells (with nuclei), like fungi or protozoa.
• B describes prokaryotic cells (no nuclei), like bacteria.
• D describes spore-producing eukaryotes, like certain fungi.

Final answer: C