Viral Structural Components

Steps:

• Identify core viral elements: genetic material (nucleic acid) and protein capsid.
• Note optional viral feature: lipid envelope in enveloped viruses.
• Exclude non-viral features: cellular organelles or metabolic machinery.
• Match diagram: 1 (nucleic acid), 2 (capsid), 4 (envelope) fit viruses; 3 (e.g., ribosome) does not.

Why B is correct:

• Viruses are defined as acellular entities with nucleic acid (1), protein coat (2), and sometimes envelope (4), per standard virology.

Why the others are wrong:

• A includes 3, a cellular component viruses lack.
• C excludes 2, the essential protective capsid all viruses have.
• D excludes 1, the genetic material central to viral replication.

Final answer: B