There are various ways to underline text. You can underline text with a single line, a double line, a dotted line or even choose to underline only the words (not the spaces). To select which type of underlining you want, use the Font option in the Format menu. The following dialogue box will appear:

When you click on the down arrow in the Underline box, you can see a list of all the types of underlining available. Select the type you want, then click on OK.