When a student completes a question in a participation activity, an orange banner appears to indicate completion.
When the student completes all of the questions in a question set, the banner in the top corner of the activity will become orange.
The completion icons on the side remain filled in, though, so students can know what activities have already been completed.
The zyBooks system intentionally does not show previous answers to learning questions. That way, students can redo a section to help better learn the material.
Research shows that this approach is better for learning (one article discussing such research).
For certain participation activities, students are able to click the "Show answer" button to easily review the correct answer.