Which term is a microscopic infectious agent?

• A. Volume
• B. Verbal
• C. Virus
• D. Vital

Answer: (C)

The main idea is to recognize something that is both infectious and microscopic. A virus fits this description: it’s a tiny infectious particle made of genetic material wrapped in a protein coat and is too small to see with the naked eye. Viruses can only replicate inside living cells, using the host’s machinery, which is a hallmark of infectious agents. The other terms don’t describe infectious particles at all—volume is a measure of space, verbal relates to speech, and vital means essential or alive, not a microscopic infectious agent.