Clarify how to mark up binomials

[samimaattaCelia]

Binomials are marked up using <mfrac> and with the attribute linethickness='0'. Example:

<math>
  <mrow>
    <mo>(</mo>
    <mfrac linethickness="0">
      <mi>n</mi>
      <mi>k</mi>
    </mfrac>
    <mo>)</mo>
  </mrow>
</math>

Results in $\binom{n}{k}$.

Edit: typo in mark up.

[Lisahartun]

Isn't this clarified?
I'm looking at: https://w3c.github.io/mathml-core/docs/explainer.html
Where it states:
Layout/Relationship elements mrow(for grouping sub-expressions), mfrac (for fractions and fraction-like objects such as binomial coefficients and Legendre symbols), msqrt and mroot for radicals

[samimaattaCelia]

True. Do you think it could be a challenge for the suppliers to get it right? This is the main reason I thought that this could be included in the guidelines.