Explanation: To add up a series of numbers in a spreadsheet application, the button you typically click is (1) The autosum button. The autosum button is designed to automatically calculate the sum of a range of selected cells. It is commonly represented by a sigma symbol (?) and is usually located on the toolbar or ribbon of the spreadsheet application. By selecting the range of numbers you want to add and then clicking the autosum button, the application will insert a sum formula that calculates the total of the selected cells. Therefore, the correct option is (1) The autosum button.