Create an Interactive Quiz in PowerPoint
If you post PowerPoint slides for your students to review, another potentially useful option is to insert interactive quiz questions into the PowerPoint file. Students can then look at the slides in slide show mode online or after they have downloaded them, and the quiz questions will provide an interactive feature.
From the Mix menu click on the Quizzes button. 
If you are not brought to the "store" automatically, click on the button to go to the online store. Note that you can choose several types of questions, and there are also options to insert videos.
The video below is a brief tutorial on how to insert quiz questions into a PowerPoint presentation.
The link below will open an 11 slide PowerPoint file in which slide #9 has a multiple choice question, slide #10 has embedded questions on ratios from the Khan Academy collection, and slide 11 as an embedded video on influenza vaccines from the Khan Academy (downloaded from the "Lab Apps Store.")
Link to Demo Quiz in PowerPoint