Beginning with the version of exerquiz dated 2018/02/07, the package now supports partial corrections of MC and MS questions.
The default behavior of quizzes created by the quiz environment is to fully correct the quiz. For MC and MS questions, this means markers for correct answers are displayed and any incorrect answers are marked as wrong.
You can change this default behavior to only partially correct the quiz; this means that only the choices the respondent has made are marked as either right or wrong, the other entries in the choice field are left untouched.
Read more by saving correct-fully-OnOff.pdf to your own computer and opening with the Adobe Reader (or Adobe Acrobat) application. The new generation of browsers do not support the Adobe Reader plugin.