Which of the following is used to apply styles to HTML elements?

The choice of CSS as the correct answer stems from its foundational role in web development as a stylesheet language specifically designed to describe the presentation of HTML elements. CSS (Cascading Style Sheets) allows developers to apply styles such as colors, fonts, layouts, and positioning to web pages, enabling the separation of content (HTML) from design.

By utilizing CSS, one can create visually appealing and responsive designs that can be easily maintained and altered without changing the underlying HTML structure. This capability helps streamline the development process and enhances the overall user experience on the web.

In contrast, while JavaScript can manipulate the style of elements through the Document Object Model (DOM), its primary purpose is to add interactivity and functionality to web pages rather than purely style them. HTML serves as the backbone structure of a webpage and does not inherently define styling properties. XML, on the other hand, is a markup language used to store and transport data, without any styling capabilities directly associated with it. Thus, CSS distinctly stands out as the appropriate choice for applying styles to HTML elements.