<math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\ce {H2O}}">
  <semantics>
    <mrow class="MJX-TeXAtom-ORD">
      <msubsup>
        <mtext>H</mtext>
        <mrow class="MJX-TeXAtom-ORD">
          <mn>2</mn>
        </mrow>
        <mrow class="MJX-TeXAtom-ORD">
          <mspace width="0pt" height="0pt" depth=".2em" />
        </mrow>
      </msubsup>
      <mtext>O</mtext>
    </mrow>
    <annotation encoding="application/x-tex">{\ce {H2O}}</annotation>
  </semantics>
</math>