Which statement about viruses is true?

• A. They are always killed by vaccines.
• B. They are bacteria.
• C. They have no nucleic acids.
• D. They are not living organisms.

Answer: (D)

Viruses are not living organisms because they can’t carry out life processes on their own. They lack the cellular machinery and energy pathways that living cells use, and outside a host, they’re just inert particles. They rely on a host cell to reproduce, hijacking the cell’s machinery to copy their nucleic acids and make viral proteins. This dependence on a host is what distinguishes them from living organisms, even though they do contain genetic material (DNA or RNA) and a protein coat.

The other statements don’t fit: vaccines don’t always kill viruses—they work by teaching the immune system to recognize and neutralize them, and some vaccines use inactivated or weakened forms of the virus; viruses are not bacteria since bacteria are living cells with their own metabolism and structure; viruses do have nucleic acids, so saying they have none is false.