[examination points] this question mainly examines the number of years of compulsory education.

[Detailed explanation of famous teachers] China implements nine-year compulsory education. Compulsory education is a national education that school-age children and adolescents must accept according to law and is guaranteed by the state, society and family. Its essence is a system of compulsory education for school-age children and adolescents for a certain period of time in accordance with the provisions of the law. China's Compulsory Education Law stipulates that the length of compulsory education is nine years, which is in line with China's national conditions. Therefore, the correct answer to this question is C.