Which key combination is useful for quickly summing cells in Excel?

The key combination Alt + = is a powerful shortcut in Excel that quickly inserts the SUM function to calculate the total of a range of cells. When you select a cell directly below or to the right of the range you want to sum, pressing Alt + = automatically identifies the adjacent cells containing numbers, creating a SUM formula that includes them. This functionality enhances productivity by eliminating the need to manually type out the SUM function and select the range of cells, streamlining the process of performing calculations.

In comparison, the other options do not serve the same purpose or are not standard Excel shortcuts. This efficiency and ease of use make Alt + = an essential tool for anyone looking to speed up their workflow in Excel.