Defining Viral Structure

Steps:

• Viruses are obligate intracellular parasites lacking cellular organization, confirming non-cellular structure (1).
• All viruses possess a protein capsid enclosing genetic material, verifying protein coat (2).
• Viruses contain a single type of nucleic acid—either DNA or RNA, not both—ruling out both (3) and supporting either (4).
• Cross-reference options: B combines accurate features (1 and 4) while excluding errors.

Why B is correct:

• By virology definition, viruses are acellular (1) with a genome of either DNA or RNA (4), distinguishing them from cells.

Why the others are wrong:

• A: Includes 3, but viruses never have both DNA and RNA genomes.
• C: Includes 3 (incorrect) and omits protein coat (2) and either nucleic acid (4).
• D: Omits non-cellular structure (1), a core viral trait.

Final answer: B