What is an "Anchored" option?

If your list is being randomised, a choice, statement, or header that is anchored will remain in the same position.

Anchor in Question Editor

Click the anchor icon in your question editor to anchor a choice, statement, or header in place.

Anchor in Preview

Note how the block with the blank header is anchored and the choices within that header are anchored too while the rest of the headers and choices are randomised!