It really depends on the specific goal you are trying to achieve.
If your aim is to have all h1 headings in bold, then you should go with option #2 and use CSS to apply the styling to all h1 elements.
CSS
h1 {
font-weight: bold;
}
HTML
<h1>realestate</h1>
On the other hand, if you only want certain h1 headings to be bold, then option #3 is more suitable. Use CSS to target h1 elements with the "bold" class for styling.
CSS
h1.bold {
font-weight: bold;
}
HTML
<h1 class="bold">realestate</h1>
The first approach could be considered if you specifically require only a part of the h1 text to be in bold.
CSS
.bold {
font-weight: bold;
}
HTML
<h1><span class="bold">real</span>estate</h1>
Additionally, it is important to pay attention to proper quoting and closure of tags in your code samples.