Select & Lock actions will lock in a choice based on a prior selection on the page. 

For example, let's say that the lunch box option below is required when the registrant selects Option Three. 

You would first create the options on the form. Then go into the Actions tab to set up the action below to lock in that choice. 

FAQs

The fields that are not selected will be empty. The fields that are selected will be populated with data.