Which HTML attribute is used to define inline styles?

The attribute used to define inline styles in HTML is the style attribute. This attribute allows web developers to apply CSS styles directly to HTML elements without the need for separate style sheets or style blocks.

By using the style attribute, you can include CSS properties and values immediately within an HTML tag. For example, if you wanted to change the color of a paragraph to red, you could write <p style="color: red;">This is a red paragraph.</p>. This inline styling applies directly to that specific paragraph only, making it a straightforward way to implement styles for individual elements on a webpage.

The other choices relate to different aspects of HTML. The class attribute is used to assign one or more class names to an element, allowing it to inherit styles defined in CSS stylesheets. The id attribute assigns a unique identifier to an element, which can also be targeted with CSS, but is not used for inline styling. The term inline is not an HTML attribute but a descriptor of a style application method; thus, it does not directly define any styles. Therefore, the style attribute is the correct choice for defining inline styles.