I feel that science and engineering courses, mathematics majors, real variable functions, structural mechanics of civil engineering, electromagnetic fields and electromagnetic waves of communication engineering are all communicated by myself, and no one in the class can understand them at all. Principles of medical pharmacology, chemical engineering, physical chemistry and chemical engineering. There are too many other high numbers, C language, line generation, probability statistics, analog electricity and high-frequency electronic circuits, and my experience is limited. I hope you will forgive me. Many other majors are also difficult.