The Recent Workbooks list in the Backstage View shows all workbooks recently opened. What action can you take to ensure a workbook remains on this list regardless of how many workbooks are opened subsequently?

1) Save the workbook to the Recent Workbooks folder.
2) Add the workbook to My Favorites on the Quick Access Toolbar.
3) The Recent Workbooks list automatically keeps all workbooks that have been opened, so no action is needed.
4) 'Pin' the workbook to the Recent Workbooks list by clicking the pin icon next to it.