Problem:
You want to add underline, may be under a text, using HTML only, no CSS.
Solution:
Use <u> and </u> tags to add underline in HTML. Put the text that you want add underline between the tags. Check the following code-
Lorem ipsum dolor sit amet, <u>consectetur adipiscing elit.</u> Donec in lectus non purus fringilla finibus.
Output:
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec in lectus non purus fringilla finibus.
Note: You shouldn’t use <u> tag to underline text for presentation purpose. This tag is not intended to use for this purpose in latest html version. Instead use CSS for this.