Which of the following is NOT a common source of foodborne illness?

High-quality, imported ingredients themselves are generally not considered a common source of foodborne illness. While imported foods can potentially be contaminated, the quality of the ingredients—if handled and cooked properly—should not inadvertently lead to foodborne illness. The focus on high-quality foods often implies that they meet certain safety and handling standards, which decreases the likelihood of contamination compared to food that is not produced under such standards.

On the other hand, improper cooking temperatures, contaminated water supplies, and inadequate refrigeration are well-documented factors that can contribute to foodborne illnesses. These issues can lead to the survival or growth of pathogenic microorganisms in food, directly increasing the risk of illness. Therefore, while the source and quality of ingredients are important in food safety, high-quality imported ingredients are not commonly linked to foodborne illnesses when proper food safety practices are observed.