1, the real questions for the postgraduate entrance examination generally originated from the research and recruitment office. The admissions office of this school can definitely buy it, but generally it won't answer again.
The copy room in this school usually gets the real questions from the research and recruitment office, and then asks students to make an answer to sell it (this answer is made by one of your seniors, so you should not expect too much from its quality). Moreover, the copy room generally has notes on postgraduate subjects, but the quality should also be identified by itself.
3. Generally, online places like Taobao and forums are sold by people. These people are either your seniors or the people in your school's copy room, and they usually add some money to sell them. After all, the money in the copy room is to sell copies, and the money online is to sell materials.
Note: Don't expect too much from the answer. Generally, it is available online and in the copy room. Essentially, it's the same. It's all made by seniors or something. It has reference value, but don't believe it completely. You'd better discuss this answer with your research friends. By the way, some schools have specialized courses offered by teachers, and the last lesson of this remedial class will generally give a more official answer to the real questions in the last two or three years. If this school doesn't open, it will be gone.
I hope it helps you. If in doubt, welcome to adopt.