What equipment is essential for protecting the practitioner when using an electric file?

The correct choice emphasizes the importance of using a dust mask when operating an electric file. An electric file produces a significant amount of dust from the nail material being filed, which can potentially be harmful when inhaled. Inhaling this dust could lead to respiratory issues or other health complications over time.

By wearing a dust mask, practitioners can protect their respiratory system from inhaling fine particles generated during the filing process. This is crucial in maintaining long-term health and ensuring a safe working environment. Other protective equipment, while useful in different scenarios, do not specifically address the respiratory risks associated with the debris created during the use of an electric file, which is why the dust mask is essential in this context.