What setting should I use if I do not want my students to be able to return to a previous question in a quiz?
Sequential is what you should use. Here is how to set it:
Go into your quiz. On the left side of the page in the Settings block click "Edit settings". Click "Show advanced' in the "Layout" section. In the “Navigation method” drop-down menu select “Sequential” in the Layout block. Students will be forced to progress through the quiz in order and will be unable to return to previous pages or skip ahead.
Save your settings at the bottom of the page.