Identify the button, on the ribbon (horizontal tabs) that can be used directly for summation of values from cells.

Auto Sum

The correct answer is option (3) : Auto Sum.

AutoSum automatically inserts a formula using the SUM function to add up values in a specified range of cells. It intelligently guesses the range you want to sum based on the cell you select. For example, if you select a cell below a column of numbers, it will automatically sum that entire column.