This articles explains what steps you have to follow to publish the feedback for a quiz. 

You have created a quiz and provided feedback for individual answers or questions. To publish this feedback to students, follow the next steps:

1. Go to Course Tools and then Quizzes, via the Navbar of your Course Homepage. 
2. Find the quiz, of which the feedback must be published. Click on the quiz.

3. Go to the Evaluation & Feedback menu

4. Open the Evaluation & Feedback menu and select the options you want.   

For more information about the Evaluation and Feedback menu go to: Quizzes - Evaluation & Feedback