Continuing education refers to non-academic education for professional and technical personnel for the purpose of updating, supplementing, broadening professional knowledge and training, and improving business capabilities. According to the above definition, which of the following is the following for continuing education? ['Educational authorities train summer socialist market economy theory teachers every summer.', 'Many college-level teachers have obtained undergraduate diplomas through correspondence education or self-study exams.', 'A university requires teachers who have obtained the title of the lecturer to enter a higher degree.', 'Labor Bureau provides various forms of vocational training for laid-off workers.']