Which condition results from injury or disease that affects the nail?

A nail disorder is indeed the correct answer because it refers specifically to any condition that arises due to injury or disease affecting the structure and function of the nails. Nail disorders can manifest in various ways, including changes in nail color, texture, shape, or growth patterns. Conditions like nail fungus, ingrown nails, or trauma-induced changes exemplify how an injury or disease can manifest as a nail disorder.

The other options don't fit this definition. A healthy nail indicates a normal, unblemished state, while nail enhancement refers to artificial improvements like acrylics or gels that do not originate from natural nail health issues. Nail maintenance involves the care and upkeep of nails to ensure they remain in good condition, but it does not pertain to conditions resulting from injury or disease. Therefore, the focus on the impact of injury or disease is key to understanding why a nail disorder is the correct choice in this context.