如何在optgroup中返回选项的文本？

ok, so this is the code

好的,所以这是代码

<select name="book" id="book">
                <optgroup label="Camus">
                <option>The Outsider</option>
                <option>The Rebel</option>
                <option>The Plague</option>
            </optgroup>
            <optgroup label="Orwell">
                <option>Animal Farm</option>
                <option>Nineteen Eighty-Four</option>
                <option>Down and Out in Paris and London</option>
            </optgroup>
</select>
<select n