You Are Creating a Web Site for a Customer

You are creating a Web site for a customer. You will use an external linked style sheet for controlling the style of elements and giving a consistent look and feel to the site. Which of the following best describes this external style sheet?

A) A text file that uses the .css file name extension and contains style definitions and HTML formatting tags
B) A text file that uses the .htm file name extension and contains only style definitions
C) A text file that uses the .htm file name extension and contains style definitions and HTML formatting tags
D) A text file that uses the .css file name extension and contains only style definitions