Which of the following products is often used to prep the nails before applying polish?

Nail primer is specifically designed for use before applying polish to ensure better adhesion and longevity of the polish. It works by removing any oils or residues on the nail surface, creating a clean slate for the polish to adhere to. Additionally, primer often contains ingredients that help bond the polish to the nail, reducing the likelihood of chipping or peeling.

In contrast, hand lotion is meant for moisturizing the skin and does not serve a purpose in preparing nails for polish application. Cuticle oil, while beneficial for nourishing the cuticles, can leave an oily residue that may actually hinder polish adhesion. Nail strengtheners are used to enhance the durability and health of the nail itself, but they do not play a role in preparing the nail surface for polish. Therefore, nail primer is the most suitable choice for prepping nails before polish application.