A. Duolingo English Test is an adaptive test due to the fact that the questions asked in it adapt to the answers that the test taker gives. Therefore, the difficulty level of the questions is set accordingly. The questions are generated by a grading system implemented by Duolingo as the test is AI-driven. So, questions are chosen by the system from a large pool of questions and no question appears twice. In order to get an in-depth idea about the DET structure, you are suggested to go through the video walkthrough on the official website.