Which product is typically applied to protect the nails before applying nail polish?

The correct choice is a base coat, which serves a crucial role in nail care before the application of nail polish. A base coat is specifically formulated to create a smooth surface on the nail, enhancing the adherence of nail polish and helping it to last longer. It acts as a barrier between the natural nail and the colored polish, preventing potential staining from pigments. Additionally, a base coat can often contain strengthening agents that help improve the health of the nails by providing added protection.

In contrast, a top coat is applied after the nail polish has been put on; its function is to seal the color and add shine while further protecting the polish from chipping. Nail polish remover is used to eliminate existing polish and does not contribute to the protection of the nail prior to applying new polish. Cuticle oil is beneficial for moisturizing the cuticles and surrounding skin but does not serve to protect the nails under polish. Thus, the base coat is essential for optimal nail preparation and care before color is applied.