If you'd like to restrict which screens of an activity students can interact with at a given time, you can use Teacher Pacing. Simply click on the Teacher Pacing icon in the bottom left hand corner of your screen within the teacher dashboard.
You will be prompted to choose the first and last screen that students will see. If you only want students to see a single screen, only select one screen. The pages that students will be able to freely access will be highlighted in blue.
On the student side, students will notice very little change other than they will not be able to move backwards or forwards from the screens that you've selected for them. On the teacher dashboard, you'll see an orange display across the top that will alert you that teacher pacing mode is turned on.
You can disable teacher pacing by selecting Turn Off or change the selected screens by clicking on the "screens 1 - 4" link in the orange display.