how to underline text in css

1h1 {
2  text-decoration: overline;
3}
4
5h2 {
6  text-decoration: line-through;
7}
8
9h3 {
10  text-decoration: underline;
11}
12
13h4 {
14  text-decoration: underline overline;
15}

1x {
2  text-decoration: line-through;
3}

1text-decoration: underline;

1h2 {
2  text-decoration: line-through;
3}

1style="text-decoration: line-through;"

1h3 {
2  text-decoration: underline;
3}