Test questions should have an internal note field for preserving information a professor might want to remember from year to year, like documenting where a correct answer is cited.
There should also be an optional explanation field that could display for incorrect answers. Basically a pre-programmed comment that, if enabled, would automatically display for all students with an incorrect answer, giving them information like an encouragement to review a specific reading -- something more than just the fact that they got the answer wrong.