Final answer:
The statement that viruses can contain either DNA or RNA but not both is true. Viruses are acellular and must infect host cells to replicate. They are not visible under a light microscope but can be seen with an electron microscope.
Step-by-step explanation:
Viruses can contain either DNA or RNA, but not both, which is a true statement. Viruses are classified into two broad categories: DNA viruses and RNA viruses, based on the type of nucleic acid that makes up their genome. Unlike living organisms that predominantly use DNA as their genetic material, viruses have adapted to have one of the two nucleic acids—either DNA or RNA—but they never have both in the same virus particle. For example, rhinoviruses that cause the common cold and the influenza virus are RNA viruses, whereas viruses like the Herpes simplex virus are DNA viruses.
Viruses are acellular, meaning they are not cells and do not possess the typical cellular structures or carry out metabolic processes on their own. They rely entirely on a host cell's machinery to replicate. Contrary to common belief, viruses cannot replicate outside of a host cell—this is a hallmark of their parasitic nature. When it comes to visualization, viruses are extremely small and cannot be seen with a light microscope; they are visible only under an electron microscope.