There are three ways to apply CSS to an HTML document: inline, internal, and external. To link an external CSS file, you must use the HTML `<link>` tag inside the `<head>` section of the HTML document.
The `<link>` tag defines the relationship between the current document and an external resource.
The correct syntax requires three key attributes:
`rel="stylesheet"`: This attribute is required and specifies the relationship. It tells the browser that the linked document is a stylesheet.
`href="styles.css"`: This attribute specifies the URL or path to the external CSS file.
(Optionally) `type="text/css"`: This attribute specifies the media type of the linked document, but it is no longer required in HTML5.
Let's analyze the options:
(A) `<link style src="styles.css">`: Incorrect. The attributes are `rel` and `href`, not `style` and `src`.
(B) `<css>styles.css</css>`: Incorrect. There is no `<css>` tag in HTML.
(C) `<link rel="stylesheet" href="styles.css">`: This is the correct syntax.
(D) `<stylesheet>styles.css</stylesheet>`: Incorrect. There is no `<stylesheet>` tag in HTML.