What items are prohibited from being placed in the mixer while it is turned on?

The correct answer highlights that hands should never be placed in a mixer while it is turned on due to safety concerns. When the mixer is operational, the beaters or blades are moving rapidly and can cause serious injury, including cuts or amputations. This protective guideline is crucial in a kitchen setting to ensure the health and safety of all employees working in the back-of-house.

The other items listed, such as metal utensils, scrapers, and wooden spoons, are typically designed for food preparation and mixing tasks. While care should still be taken with these objects to avoid damage to the mixer or risk of injury, they are not inherently dangerous when appropriately used at the correct time. In contrast, putting hands into the moving parts of a mixer poses an immediate danger, underscoring the importance of strict adherence to safety protocols in kitchen operations.