<!DOCTYPE html>
<html>
<body>
<h1>The optgroup element</h1>
<p>The optgroup tag is used to group related options in a drop-down list:</p>
<form action="/action_page.php">
<label for="cars">Choose a car:</label>
<select name="cars" id="cars">
<optgroup label="Swedish Cars">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
</optgroup>
<optgroup label="German Cars">
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</optgroup>
</select>
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>