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<!DOCTYPE html> <html> <body> <select size="6"> <option value="BMW">BMW</option> <option value="Mercedes">Mercedes</option> <optgroup id="myOptgroup" label="Swedish Cars"> <option value="volvo">Volvo</option> <option value="saab">Saab</option> <option value="koenigsegg">Koenigsegg</option> </optgroup> </select> <p>Click the button to change the value of the label attribute of the option-group.</p> <button onclick="myFunction()">Try it</button> <script> function myFunction() { document.getElementById("myOptgroup").label = "A Random Car Selection"; } </script> </body> </html>