A Radio List field, commonly referred to as multiple choice will limit the applicant to only choosing one of the available values. Great for 'Yes' / 'No' style answers.
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To add a Radio List field to your submission form, select the Radio List button from the left side panel of your form builder.

You can set the field values by clicking the + and x symbols next to the field value option. You can also click Bulk Add to add many options all at once.

Often times you may want to ask a set of questions that depend on the previous answer from the applicant.

With a radio list field, you can set your option values. Each option value will have a 'link' icon to the left that you can click. Another form builder will appear and you can create your new set of questions. You can even chain these dependent fields and go down a tree of questions.

To the end user, it functions like this:

Disable one or more radio list options for locking them. This is helpful if you want to only allow a certain number of applicants to select a value. Once you've reached your cap you can disable that item.

The option will be visible on your form, however applicants will not be able to select them: