markdown的修辞语法

Markdown使用星号和底线来标记需要细分的分段。

Markdown语法：

Some of these words *are emphasized*.
Some of these words _are emphasized also_.
Use two asterisks for **strong emphasis**.
Or, if you prefer, __use two underscores instead__.

输出HTML为：

<p>Some of these words <em>are emphasized</em>.
Some of these words <em>are emphasized also</em>.</p>
<p>Use two asterisks for <strong>strong emphasis</strong>.
Or, if you prefer, <strong>use two underscores instead</strong>.</p>