You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allpages gapcontinue="世界文學:佳節_慶祝" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1722" ns="0" title="Test a01" contentmodel="wikitext" pagelanguage="zh-tw" touched="2017-02-12T15:47:03Z" lastrevid="4576" counter="6367" length="1707" />
      <page pageid="1688" ns="0" title="UneedADV 專欄" contentmodel="wikitext" pagelanguage="zh-tw" touched="2016-04-11T08:08:56Z" lastrevid="4384" counter="2951" length="4966" />
      <page pageid="1734" ns="0" title="世界文學:2018臺灣運勢" contentmodel="wikitext" pagelanguage="zh-tw" touched="2018-02-26T09:34:15Z" lastrevid="4639" counter="1379" length="646" />
      <page pageid="1759" ns="0" title="世界文學:2018臺灣選舉" contentmodel="wikitext" pagelanguage="zh-tw" touched="2018-11-25T02:27:01Z" lastrevid="4735" counter="1231" length="812" />
    </pages>
  </query>
</api>