Answer:
The Show Desktop button
Step-by-step explanation:
In Windows 98, the button that allows you to minimize all open windows with a single taskbar click is called the "Show Desktop" button. It is located at the far right end of the taskbar and looks like a small rectangular icon with a thin horizontal line on it. Clicking on this button will minimize all open windows and show the desktop. You can restore the minimized windows by clicking the "Show Desktop" button again, or by clicking on the minimized windows in the taskbar.