s is an H1
=============

This is an H2
-------------

### 字符效果和横线等
                
----

~~删除线~~ <s>删除线（开启识别HTML标签时）</s>
*斜体字*      _斜体字_
**粗体**  __粗体__
***粗斜体*** ___粗斜体___

上标：X<sub>2</sub>，下标：O<sup>2</sup>

**缩写(同HTML的abbr标签)**

> 即更长的单词或短语的缩写形式，前提是开启识别HTML标签时，已默认开启

The <abbr title="Hyper Text Markup Language">HTML</abbr> specification is 