The correct answer is D. Underlining.
The formatting toolbar is a toolbar that contains buttons for formatting text. These buttons allow you to change the font, font size, font color, alignment, and other aspects of the text. The underlining button is used to underline text.
A. Your hard drive is not something that can be formatted using buttons on the formatting toolbar.
B. Format painting is a feature that allows you to apply a format to a selected area of text. This feature is not available on the formatting toolbar.
C. Font color is a property of text that can be changed using the font color button on the formatting toolbar.
D. Underlining is a property of text that can be changed using the underlining button on the formatting toolbar.