The excel ribbon has three modes - auto show, show tabs, and show tabs and command. which mode would you choose to enable the worksheet itself to take up the entire screen

To enable the worksheet to become full screen you would select the Auto Hide ribbon. Auto hide will display the workbook in the full screen mode and also completely hide the ribbon. The show tabs would simply hide all command groups that are not being used while the tabs remain visible, and show tabs and commands maximizes the ribbon, all tabs and commands will be visible (this is excel's default option).

Answer is Auto hide mode

As mentioned, there are three modes in the ribbon display option. The Auto-hide ribbon displays a workbook in full screen and entirely hides the ribbon. To bring back the ribbon, click the Expand Ribbon option command at the top of the screen.