How can you format a cell's border in Excel?

To format a cell's border in Excel effectively, using the Border tool in the Home tab is the most direct method. This tool allows you to customize borders by providing various options such as setting the style, color, and the specific borders to apply, including top, bottom, left, right, or all around the selected cell.

Option B, which involves right-clicking the cell and selecting Format Cells, does allow for more comprehensive formatting options, including fonts, number formats, and alignment. While you can access a border options dialog through Format Cells, it is not the most efficient or direct method for simply formatting borders when compared to using the dedicated Border tool available in the Home tab.

The other choices do not effectively lead to the desired outcome of formatting cell borders. The Fill Color button is used for background color adjustments, pressing Ctrl + B applies bold formatting to text, and right-clicking the cell does not inherently lead to border formatting unless you navigate through the additional options. Thus, the Border tool in the Home tab is the most straightforward and user-friendly method for formatting cell borders in Excel.