Answer: the icon that shows a sheet of paper and a magnifying glass
Step-by-step explanation:
The Quick Access Toolbar, gives access to the features that are usually used like Save, Undo/Redo. It can also be customized such that the commands that the users usually use can be placed quicker and therefore makes them easier to use.
After Sally adds the Print Preview and Print command to the Quick Access Toolbar, the icon that she would have added is the icon that shows a sheet of paper and a magnifying glass.