why should you list more than on font if you are formatting some text using CSS?

not every browser supports every font.
CSS will use different fonts when the page is refreshed.
CSS will select the font that best fits on the page.
all of the fonts will appear in the web page.

The correct answer is:

not every browser supports every font.

Listing more than one font in CSS allows for fallback options in case a certain font is not supported by a user's browser. If the first font listed is not available, the browser will then try the next font in the list until it finds one that is supported. This ensures that the text will still be displayed properly, regardless of the user's browser capabilities.