What type of foodborne pathogens typically require a host to complete their lifecycle?

Parasites are organisms that depend on a host to complete their life cycle, which is why they are the correct answer. These organisms often live in or on a host and can cause various health issues. For example, certain parasites may rely on the host's body for nutrients to grow and reproduce, and they cannot survive or complete their lifecycle outside of a living host organism.

In contrast, bacteria are independent microorganisms that do not require a host to grow or reproduce; they can thrive in various environments, including food and water. Yeasts and molds, which are types of fungi, also do not need a host to complete their life cycle. They typically derive nutrients from their surroundings, often growing on organic matter. In summary, while bacteria, yeast, and molds can all contaminate food and cause spoilage or illness, parasites uniquely rely on a host organism for their lifecycle, making them the correct choice in this context.