The correct answer is: B. Fill handle.
The fill handle is a small, black square in the lower-right corner of an active cell or range. It is used to fill cells with a series of values or formulas. To use the fill handle, select the cells that you want to fill, then click and drag the fill handle to the desired cells.
The copy handle is a small, black square that appears in the upper-left corner of a selected cell or range. It is used to copy cells to other locations in the worksheet. To use the copy handle, select the cells that you want to copy, then click and drag the copy handle to the desired location.
The insert handle is a small, black square that appears in the lower-right corner of a selected cell or range. It is used to insert cells into the worksheet. To use the insert handle, select the cells that you want to insert, then click and drag the insert handle to the desired location.
The border is a line that surrounds a cell or range of cells. To add a border to a cell or range, select the cells that you want to border, then click the Borders button on the Home tab of the ribbon.