What is the term used to describe any element in a style sheet that has designated styles applied to it?

The correct term to describe any element in a style sheet that has designated styles applied to it is "selector." In CSS (Cascading Style Sheets), a selector is a pattern used to select the element(s) you want to style. Selectors can target elements based on various attributes like their type, class, ID, or even their position in a document. Once an element is selected, you can apply various styles to it via a style rule.

It's important to note that a style rule consists of a selector and the declarations that define the styles to be applied. The element itself is the HTML component you are working with, while the property refers to individual aspects of the style, such as color or font-size. Thus, "selector" specifically identifies which HTML elements are targeted for styling, making it the appropriate answer in this context.