As pointed out in previous posts, you will need to create 3 separate array questions and then use CSS (and maybe JavaScript) to align them side-by-side.
The CSS and JS would depend entirely on the template being used.
Also note that things could get a little messy if you want the questions to be mandatory.
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Cheers,
Tony Partner Solutions, code and workarounds presented in these forums are given without any warranty, implied or otherwise.