Which statement correctly describes how viruses reproduce?

• A. They must invade living cells to reproduce
• B. They reproduce independently in air
• C. They replicate only in dead tissue
• D. They are free-living organisms

Answer: (A)

Viruses cannot make more of themselves without a living cell. They lack the full set of cellular machinery—like ribosomes and metabolic enzymes—needed to copy their genetic material and assemble new viruses. Instead, a virus must enter a living host cell and hijack that cell’s machinery to replicate viral components, assemble new virions, and then release them to infect other cells. Outside a living cell, viruses are essentially inert and do not reproduce in air, on surfaces, or in dead tissue. This dependence on a host cell is why they’re described as obligate intracellular parasites.