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>
    <allcategories accontinue="06._In-channel_structure_and_substrate_improvement" />
  </query-continue>
  <query>
    <allcategories>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">01. Water abstractions</c>
      <c size="9" pages="9" files="0" subcats="0" xml:space="preserve">01. Water flow quantity improvement</c>
      <c size="6" pages="6" files="0" subcats="0" xml:space="preserve">02. Flow regulations</c>
      <c size="7" pages="7" files="0" subcats="0" xml:space="preserve">02. Sediment flow quantity improvement</c>
      <c size="9" pages="9" files="0" subcats="0" xml:space="preserve">03. Flow dynamics improvement</c>
      <c size="3" pages="3" files="0" subcats="0" xml:space="preserve">03. River fragmentation</c>
      <c size="6" pages="6" files="0" subcats="0" xml:space="preserve">04. Longitudinal connectivity improvement</c>
      <c size="8" pages="8" files="0" subcats="0" xml:space="preserve">04. Morphological alterations</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">05. Other hydromorphological pressures</c>
      <c size="6" pages="6" files="0" subcats="0" xml:space="preserve">05. River bed depth and width variation improvement</c>
    </allcategories>
  </query>
</api>