The content of elective courses on the college entrance examination paper is optional, such as general chemistry, and there are three books for candidates to choose from, such as chemistry and technology, material structure and properties, and organic chemistry foundation. It should be noted that some elective courses are compulsory, such as the principle of chemical reaction in chemistry, and physics and biology are similar. Mathematics is also an elective course, and the elective course of college entrance examination is not absolutely free.