PreTeXt exercise made up syntax

imaginary-pretext-mc.xml

<exercise>
  <statement>
    <p>
      Which of these numbers are even?
    </p>
    <multiple-choice select="many">
      <choice correct="true"><m>-4</m></choice>
      <choice><m>-1</m></choice>
      <choice correct="true"><m>0</m></choice>
      <choice><m>5</m></choice>
      <choice correct="true"><m>8</m></choice>
    </multiple-choice>
  </statement>
  <answer>
    <!-- could be interpreted from the choices? -->
    <p><m>-4,0,8</m></p>
  </answer>
  <solution>
    <p>Here is a long-winded explanation of why these numbers are right...</p>
  </solution>
</exercise>
<exercise>
  <statement>
    <p>
      Which of these numbers is <m>5-6</m>?
    </p>
    <multiple-choice select="single">
      <choice><m>-4</m></choice>
      <choice correct="true"><m>-1</m></choice>
      <choice><m>0</m></choice>
      <choice><m>5</m></choice>
      <choice><m>8</m></choice>
    </multiple-choice>
  </statement>
  <answer>
    <!-- could be interpreted from the choices? -->
    <p><m>-1</m></p>
  </answer>
  <solution>
    <p>Here is a long-winded explanation of why this was right...</p>
  </solution>
</exercise>