Returning to education is a process that believes that people's life should be a continuous and alternating process of learning and work. Adults who receive compulsory education or basic education or even after higher education should have the opportunity to return to school to study when needed. Li Ren. Which of the following types of education is a return education? ['Nine-year compulsory education.', 'A technician from a factory recharges English at the staff night school held by the unit.', 'Pre-schooler education.', 'Secondary vocational school students participate in a one-year internship after two years of full-time study.']