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For a homework assignment, simply hit the little pencil click anywhere in the blank space corresponding to the offending question:
Additionally, on this page you can provide feedback about the problem with the question by hitting the little flag icon. That will take you to a page where you can indicate how we can fix the question for future usage: Reporting an error in a question.
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You can choose to withdraw the question and give full credit to maintain the same total assignment grade, or to simply take it off as if it never existed. Don't worry either action will preserve the students' submissions on the "View Submissions" page.
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For a learning module, simply go to the question's slide and select withdraw at the bottom of the page and save the slide. It acts the same as for homework assignments.
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