Virus Composition: Nucleic Acid, Protein, and Optional Envelope

Steps:

• Viruses contain genetic material (DNA or RNA, not both) and a protein capsid; they lack carbohydrates.
• Eliminate options with carbohydrates or missing protein.
• Select options with one nucleic acid type and protein present.
• Allow phospholipids for enveloped viruses but exclude other inconsistencies.

Why D is correct:

• D fits an enveloped DNA virus: DNA genome in protein capsid with phospholipid envelope, no RNA or carbohydrates, per viral structure definitions.

Why the others are wrong:

• A lacks protein and includes carbohydrate, impossible for viruses.
• B has both DNA and RNA plus lipid without protein, violating single-genome rule.
• C has no nucleic acid, essential for viral replication.

Final answer: D