<div class="header">
    <div class="box">
        <h1>Header</h1>
    </div>
    <div class="box">
        <h2>Sub-header</h2>
    </div>
</div>
在给定的html部分中找到所有带有类"box"的元素,并删除它们.
After removing all the elements with the class "box", the resulting HTML section looks like this:

```
<div class="header">
</div>
```