Final answer:
In food preparation, the only permissible jewelry is a plain wedding band, as it poses less risk for contamination and physical hazards compared to other jewelry like necklaces, bracelets, and watches.
Step-by-step explanation:
When prepping foods, the only piece of jewelry that may be worn according to most health and safety regulations is a wedding ring. This exception is often due to the fact that wedding bands are typically smooth and without stones or intricate designs where food particles can become trapped, thus minimizing the risk of contamination. In contrast, necklaces, bracelets, and watches are not usually allowed because they have greater potential to harbor bacteria and may also pose a physical hazard if they come into contact with kitchen equipment or food.