?

看圖 ? 我的理解是level-2的子元素會變紅，但是為什么level-3也會變紅，level-3應該是子孫不應該變紅的吧

<ul?class="level-1">
??<li?class="item-i">I</li>
??<li?class="item-ii">II
????<ul?class="level-2">
??????<li?class="item-a">A</li>
??????<li?class="item-b">B
????????<ul?class="level-3">
??????????<li?class="item-1">1</li>
??????????<li?class="item-2">2</li>
??????????<li?class="item-3">3</li>
????????</ul>
??????</li>
??????<li?class="item-c">C</li>
????</ul>
??</li>
??<li?class="item-iii">III</li>
</ul>
<script>$('ul.level-2').children().css('background-color',?'red');</script>