One scenario The textbook company provides the instructor with multiplechoice tests , saving the instructor from having to create his own questions . These tests are located on a website so the computer can automatically grade them . To use the website to take a test , you must enter a key code . To get the key code , you must buy the textbook . The key code expires after use . <| sep |> well yea that ' s why i ' m giving credit to both of you <| sep |> It ' s like Orys is trying to get red wedding ' d <| sep |> ummmm i need to see a picture and i want to know where you got them lololol <| sep |> This is the truth . <| sep |> how the hell is houston not connected to any other tx city ? <| sep |> Eucl 3 d is the official printer , however , it ' s possible to 3 D print your own using Blender and a couple of plugins for it found through Google .