What is a basic characteristic of a virus?

A basic characteristic of a virus is that it requires a living host to grow. Viruses are unique compared to other pathogens like bacteria because they cannot replicate or grow independently; they need to invade a host cell to reproduce and carry out their lifecycle. This dependency on living cells is a defining feature of viruses, which differentiates them from other microorganisms that can grow and multiply in various environments, including food.

The other options do not accurately describe viruses. For instance, viruses do not grow in food or any other medium outside of a host, and they cannot be killed simply by cooking, as some viruses are heat-resistant. In addition, viruses are not single-celled organisms; they lack cellular structure altogether, existing instead as a collection of genetic material and protein. Understanding these characteristics is crucial for food safety and preventing the spread of viral infections in food service settings.