The order of difficulty is: advanced mathematics A, advanced mathematics B, advanced mathematics C, advanced mathematics D .. No E. Advanced mathematics A is an important basic theoretical course required by science (non-mathematics) students. Advanced Mathematics B is an important basic theoretical course for engineering undergraduates. Advanced Mathematics C is a compulsory basic theoretical course for students majoring in engineering (such as architecture and urban planning) and engineering colleges who have low requirements for mathematics. Advanced Mathematics D is a compulsory basic theory course for students who have lower requirements for mathematics (such as liberal arts majors).