Generally speaking, it is from trigonometric function, probability statistics, solid geometry, function (usually derivative), conic curve, sequence and so on. Moreover, the last two finale questions require very high skills, which are not easy to think of, and the time is tight and it feels abnormal. If I have enough time and a relatively high level, it is not difficult to find a breakthrough. The questions are all written by people, usually a lot. O(∩_∩)O~