6 files declare their use of QuizQuestionType in Quiz 6.x

QuizQuestionEntityForm.php in src/Form/QuizQuestionEntityForm.php

QuizQuestionListBuilder.php in src/Config/Entity/QuizQuestionListBuilder.php

quiz_long_answer.module in question_types/quiz_long_answer/quiz_long_answer.module

Long_answer question type for the Quiz module.

quiz_matching.module in question_types/quiz_matching/quiz_matching.module

Matching question type for the Quiz module.

quiz_multichoice.module in question_types/quiz_multichoice/quiz_multichoice.module

Contains quiz_multichoice.module

quiz_short_answer.module in question_types/quiz_short_answer/quiz_short_answer.module

Short_answer question type for the Quiz module.