Universal non-cellular nature of viruses

Steps:

• Define viruses as infectious agents lacking cellular organization.
• Eliminate B: Genome is DNA in some viruses (e.g., herpesviruses) but RNA in others (e.g., picornaviruses).
• Eliminate C: Phospholipid envelopes occur only in enveloped viruses (e.g., HIV); non-enveloped viruses (e.g., poliovirus) lack them.
• Confirm D: No virus possesses cells, membranes, or organelles.

Why D is correct:

• Biological definition classifies viruses as non-cellular assemblies of nucleic acid and protein that require host cells for replication.

Why the others are wrong:

• A: All viruses possess a protein capsid, but this structural detail varies in composition and symmetry, unlike the absolute non-cellular trait.
• B: RNA viruses comprise over half of known types, excluding DNA-only.
• C: Approximately 60% of viruses are non-enveloped, lacking phospholipids.

Final answer: D