Concept:Shift + F9 is used to recalculate only the selected worksheets in the active workbook, not all open workbooks.Explanation:In Excel, pressing Shift + F9 triggers a targeted recalculation. It recalculates only the active or selected worksheets within the current workbook. This is different from F9, which recalculates all worksheets in the active workbook. Using Shift + F9 saves time and improves performance when working with large datasets. It avoids unnecessary processing of unrelated worksheets or other open workbooks.Answer:A. Calculate active/selected worksheets in the active workbook.