General difficulty comparison: number A> height number B > Advanced Mathematics C> Advanced Mathematics D. Arithmetic A is an important basic theoretical course for students majoring in science (non-mathematics). Mathematics B is an important basic theoretical course required by engineering undergraduates. Mathematics C is a compulsory basic theory course for engineering undergraduates (such as architecture and urban planning) and engineering students who have low requirements for mathematics. Math d, etc. It is a compulsory basic theory course for students with low requirements for mathematics (such as liberal arts majors). Equal mathematics high number generally refers to advanced mathematics, which refers to a more complicated part of mathematical objects and methods compared with elementary mathematics.