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You cannot directly edit the Answer Choices of a survey question that uses Shared Answer Choices.
Instead you must edit the Answer Choices of the Master Question and this will then automatically edit the Answer Choices of the questions that use Shared Answer Choices that are anchored to the Master Question
Steps
Select My Apps in the top menu
Select Lists
You arrive in the Lists App
This displays:
List fields you have created from within the Lists App
Every Master Question that your Multiple Choice survey questions with Shared Answer Choices are based on
Every Multiple Choice survey question that you have created from scratch (i.e. not using Shared Answer Choices)
Click Edit to edit the List you want to change the Answer Choices within
You arrive on the Edit List page
From here you can
Add additional Answer Choices
Reorder the Answer Choices: Note: do this by changing the priority number rather than by cutting & pasting the answers themselves
Remove Answer Choices
Once you are done editing, press Save
That’s it.
If you edited a Master Question with linked Multiple Choice Questions with Shared Answer Choices, the linked Multiple Choice Questions will automatically have their Answer Choices changed in every survey they appear in.
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Summary
This functionality allows you to extend a single choice field in a survey or a multiple choice field in a survey. You can expand the survey field to include additional options and answer choices after you have initially published and created it.