Hi Mark,
Thank you for your inquiry about changing the Correct Answer on an Item in Mastery Connect.
Generally speaking, material changes to Items are not allowed after an Assessment has been administered due to the complexity of re-scoring all responses. Any Reports previously generated and distributed, would no longer be accurate.
Many folks take advantage of the Draft mode for both Items and Assessments for a review process, prior to publishing.
Further Support on this, or any other matter Mastery Connect, is available by clicking on the Question Mark to the left of your name > then Submit a support request.
Thank You
MC Support