I would like to say that such a design (multiple question types in an array) can not be used on small screens.

Smartphones represent more than 50% of users today. IMHO: You'd rather stop using arrays in your survey design.

hi, not easy to do without arrays. It is an important part of survey methodology...
thanks for the advise though !

Holch,
it is ok, the options to create columns ("answer options") are at the very bottom of the page "set subquestions", after having set the items (subquestions).
Usually "subquestions options" and "answers options" are not in the same page. so I was not looking so down in the page...
thanks again !