hr标记在其包含元素的宽度上添加水平线。这可用于定义主题更改或直观地分隔内容组。 h4下面添加一个hr标签,其中包含卡片标题。 注意 hr是一个自动关闭标记,因此不需要单独的结束标记。 hr标记。
    testString: 'assert($("hr").length == 1, "Your code should add an hr tag to the markup.");'
  - text: hr标签应位于标题和段落之间。
    testString: 'assert(code.match(/<\/h4>\s*?/gi), "The hr tag should come between the title and the paragraph.");'
```
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