If a change was made to an assessment's details (i.e. questions or answers) after students made submissions, you can re-grade the assessment based on the edited assessment.
Here are the steps to be able to do that:
1. Click Manage > Assessments
2. Click the "View/Edit Submissions" icon.
3. On the right-hand side of the page, click the "Tools" button and from the drop-down menu click on "Recalculate Grades"
4. Once this action is confirmed, you will see a progress bar appear at the bottom of the page.
5. Once the process is complete, the progress bar will turn green.
6. Click the bar, and select the option to "See New Grades."
Congratulations! You re-graded the assessment.