Which of the following is a valid HTML reference to a CSS file?

This task contains the radio buttons and checkboxes for options.

The shortcut keys to perform this task are A to H and alt+1 to alt+9.

A.

B.

C.

D.

C

Explanation:

The above code is self explanatory. All others have wrong rel or title. Title is always stylesheet, and rel as well stylesheet as well as href is external css file which we are loading, and text/css is always the type as it is the css. None of the other has this syntax. And hence this is the right answer.