Which of the following is a common source of cross-contamination?

The correct choice highlights that using different cutting boards for raw meat and vegetables is a common source of cross-contamination. Cross-contamination occurs when harmful bacteria spread from one food item to another, which can lead to foodborne illnesses. In the context of food preparation, raw meat often contains bacteria that can contaminate other foods, particularly ready-to-eat items like vegetables.

By using separate cutting boards for raw meat and other foods, such as vegetables, one significantly minimizes the risk of transferring bacteria from the meat to the vegetables. Cutting boards are often not properly sanitized between uses, so if the same board is used for both, there's a higher likelihood of cross-contamination.

The other choices represent best practices in food safety rather than sources of cross-contamination. Washing hands before handling food, cooking food to the appropriate temperature, and chilling foods promptly after cooking are all critical steps in preventing contamination and ensuring food safety. They serve to protect food from becoming unsafe, but they do not involve the direct mixing or transfer of contaminants between different food items, unlike using the same cutting board for different types of food.