Why are preschool-aged children at a higher risk for food-borne illness?

Preschool-aged children are at a higher risk for food-borne illness primarily because their immune systems are still developing and are not as robust as those of older children and adults. This vulnerability makes them less capable of fighting off harmful pathogens that can be present in contaminated food. Young children often lack the necessary antibodies and other defenses that help prevent infections, which increases their susceptibility to food-borne illnesses.

As for the other options, while factors such as dietary preferences, exposure levels, and activity might contribute to risk in different ways, they do not directly address the specific immune system weaknesses that make preschoolers more prone to serious health issues resulting from food contamination.