I recommend you to buy real questions. Writing pictures in English is very helpful for us to learn English. Using real questions to summarize the test papers of CET-4 and CET-6 in recent years, we will find that the focus of the exam is basically relatively fixed. The proposers of the test paper are all experts, and they have repeatedly deliberated and thought about each topic. Such a set of test papers is certainly not as good as a set of simulated test papers, and it is more valuable in thinking mode.
In the process of putting forward real questions, the expert editorial board studies the thinking and habits of candidates, so many seemingly simple questions are very easy to make mistakes. More often, we will insist on doing the questions according to our own ideas, and we can't jump out of our own thinking at all. Even after a long separation, I still can't see where I am wrong. This is the train of thought that the real question can bring, which is worth our study. Only by doing real questions can we really sum up the rules and skills of some questions. By practicing the real questions, we can really check the leaks and fill the gaps, and further adapt to the difficulty and type of questions. In the end, you will find that the focus is always the key, but the way of setting questions changes every year.