Final answer:
Stud earrings are usually the only kind of jewelry approved for wear in prep areas of a foodservice operation due to their minimal risk of contaminating food.
Step-by-step explanation:
In the context of a foodservice operation, it is vital to minimize the risk of contamination and ensure food safety. Among the jewelry options listed, the only type that is generally approved for wear in prep areas is d. Stud earrings. This is because they are small and less likely to harbor bacteria or fall into food compared to larger pieces of jewelry like rings, watches, and necklaces. However, policies may vary by workplace, and some places may have a 'no jewelry' policy to further reduce the risk of contamination.