Which scientific term best matches this description: Infectious agent composed of proteins and genetic material (either DNA or RNA) that requires being in a host cell, such as a plant, animal, or bacterium, in order to reproduce?

A) Virus

B) Parasite

C) Bacterium

D) Biofilm

Answer: A

Explanation: An infectious agent composed of proteins and genetic material (either DNA or RNA) that requires being in a host cell, such as a plant, animal, or bacterium, in order to reproduce. A virus is neither a cell nor a living organism because it can't reproduce on its own.