Knowing English well these days is often not enough; you need to demonstrate that you know English by having some kind of certificate. To pass these exams, you need to study a great deal and you should spend some time training for the actual exam by doing exercises from previous exams. Beyond this, there are some strategies that you can adopt that will ensure that you don’t needlessly lose points.
One of these strategies is to use “which” or “who” instead of using “that”. The problem with using “that” is that it is only correct in defining relative clauses whereas “who” and “which” are correct in both defining as well as non-defining relative clauses. If you are not 100% clear as to what the difference is, you should always use “which” and “who” so you don’t use “that” incorrectly.
Additionally, make sure that when you are doing the part of the exam in which you have to rephrase a sentence, check that the tense of the original sentence matches the tense of your sentence. Candidates will often use too much imagination and change the tense without even realizing it. You can prevent this from by double-checking your answers.