How do I prevent multiple choice grid options being hidden like in the image below?
In this case the 4th option is hidden and the horizontal scrollbar isn't shown, what might drive users think that there's only 3 options.
Short answer
I'm afraid that the Google Form web app doesn't offer an automatic way to prevent that some grid choices being hidden as is shown in the OP image. One alternative among others is to have two sections, one for large screens and another for small screens.
Explanation
Many of the elements of Google Forms are "responsive" (adapts to the screen size) but the grid questions are not yet able to adjust to small screens like the ones of mobile phones. At this time, the new Google Forms web app doesn't offer advanced options to customize the respondent view of a Google Form. I don't know how to customize the new Google Forms but it's possible to change the form to the old Google Forms app, then get source code of the respondents view and customized it, but you should find a host for the customized respondent view form file. For details, see the "Customize Google Forms" reference:
