Which of the following is NOT considered a liquid nail product?

Nail files are tools used for shaping and smoothing the edges of nails, rather than being a product that is applied to the nail or enhances its appearance. The primary purpose of a nail file is to physically manipulate the nail's surface, while liquid nail products involve substances that are applied in liquid form, such as nail polish, base coat, and nail glue, which serve specific functions related to nail enhancement or maintenance.

Nail polish provides color and finish to the nails, a base coat serves as a protective layer to prevent stains and improve adhesion, and nail glue is used to bond tips or repair breaks. Each of these is a liquid formulation that plays a role in the aesthetics or structural integrity of nails, distinguishing them from the solid, non-liquid nature of a nail file.