In Classic quizzes (which I insist on using until they make adjustments to New quizzes), you can check the box that allows students to see their responses, but not allow them to view the correct answers. I would like students to know which ones they got wrong though. Otherwise, on their second attempt they change answers that they had right and aren't sure where to focus. It'd be even better if it saved their correct answers so they didn't have to start over on those. This is especially an issue on questions with multiple blanks and dropdowns, but from what I've observed also elsewhere.