I want to note that you can achieve this result with the Checkbox custom field. In order to achieve your desired scenario, you can go to the Quiz Maker plugin > Custom Fields page and create a new custom field by clicking on the Add New button and choosing the Checkbox type.
By this, you can show the Agree to the Privacy Policy checkbox and the users need to tick it. In order to show it, you need to go to the Quizzes > particular quiz > User Data tab > Information Form option, take this custom field from the Available Fields and insert it into the Active Fields. You can make it required.