Easy going. Declare a variable name in ML, and use that name for all of your HTML-variables + an identifier.
Easy example for a 2 item questionnaire with 2 answering options (in the example, I use radio bottons, as you can see):
<input type="radio" name="nbp_01" value="1">
<input type="radio" name="nbp_01" value="2">
<input type="radio" name="nbp_02" value="1">
<input type="radio" name="nbp_02" value="2">
The variable name in the ML questionnaire is "nbp" and you use the HTML-item-type. The identifier is "_xx")
In my example, you should find two variables in your data output, a "nbp_01" + value from the subject and a "nbp_02" + the value from a subject.
Normally, this works.
best,
Tom
P.S. I guess there is a tutorial and an example about stuff like this which is shipped with ML..?