Final answer:
To allow another user to manipulate some cells in a worksheet, those cells must be left unprotected, which means they are editable and not hidden or locked by default. The correct multiple-choice option is (a).
Step-by-step explanation:
If you wish to allow another worksheet user to manipulate some cells, you should leave those cells unprotected. When a cell is unprotected, it can be edited by anyone who has access to the worksheet. By default, all cells in a worksheet are locked, meaning they cannot be edited without first removing the protection.
In contrast, hiding cells makes them invisible to the user, and formatting cells relates to visual presentation, such as font size or color. To allow edits, you typically go into the worksheet protection features and specify which cells to leave unprotected for user interaction. The correct multiple-choice option is (a).