Custom form – select entity

Hello,

I’m new to the plugin.
I created a custom form to create new contacts.
In this form, I want to display a dropdown list for contacts to choose their nationality.
I get the list of nationalities via a FetchXML query that I display in the select tag.
The nationality field in the crm is linked to an entity, emn_nationalite.
In the contact entity, the nationality field is called “emn_nationalite_id”.
In the entity nationality, the ID is in the field “emn_nationalite_id” and the name of the nationality corresponds to the field “emn_name”.
The contact is created well when I submit the form but the nationality field remains empty in the CRM.
How can I ensure that the nationality is correctly transmitted to the CRM?

Here is my code:

[msdyncrm_twig]
{% form entity="contact" mode="create" required=["lastname", "emailaddress1", "description"] %}
<form method="POST">
<label for="firstname">First Name:</label>
<input name="firstname" required="" placeholder="First Name">
<label for="lastname">Last Name:</label>
<input name="lastname" required="" placeholder="Last Name">
<label for="mobilephone">Phone Number:</label>
<input name="mobilephone" type="tel" placeholder="Phone Number">
<label for="emailaddress2">email:</label>
<input name="emailaddress2" type="tel" placeholder="email">
<label for="nationalite">Nationalité:</label>
<select name="emn_nationalite_id">
 {% for a in nartionality.results.entities %}
        <option value ="{{a.emn_nationaliteid}}">{{a.emn_name}}</option>
      {% endfor %}
</select>

<button type="submit">Submit</button>
</form>
{% endform %}

[/msdyncrm_twig]