     <optgroup label="Swedish Cars">
            <option value="volvo">Volvo</option>
            <option value="saab">Saab</option>
        </optgroup>
        <optgroup aria-activedescendant="button1" label="German Cars">
            <option value="mercedes">Mercedes</option>
            <option value="audi">Audi</option>
        </optgroup>
    </select>

    <select>
        <option value="volvo" aria-activedescendant="button1" disabled="true">Volvo</option>
        <option value="saab">Saab</option>
  