Because the curriculum books are really detailed and extensive. For someone who learned lots of the concepts in school, they just need to go over the notes. Only when they don't understand anything in the notes, they go back to the curriculum. Be careful though, the notes are written in such a casual manner that I found many errors in it. So anything confusing, trust the official curriculum!!!!
I just past level I this past June. My feeling is that level I has nothing in dept. It doesn't test much deeply and comprehensively you know all the concepts. As long as you kind of understand and remember it, you are fine. But it does test an extremely broad spectrum of things.
Good luck!!!! (Sorry can't type in Chinese in my school computer).

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tks~~~~~~~~~~

这么老的帖子。。