Create a simple quiz for each video
You can use the Webform module to create a quiz.
Here is a quote about it (from the module's project page):

Webform is the module for making surveys in Drupal. After a submission, users may be sent an e-mail &quot;receipt&quot; as well as sending a notification to administrators. Results can be exported into Excel or other spreadsheet applications. Webform also provides some basic statistical review and has and extensive API for expanding its features.
Some good examples could be contests, personalized contact forms, or petitions. Each of these could have a customized form for end-users to fill out. If you need to build a lot of customized, one-off forms, Webform is a more suitable solution than creating content types and using CCK or Field module.