Answer: elite stage (gross enrollment rate < 15%): going to college is the privilege of a few people; Shaping people's mind and personality, and cultivating officials and academic talents;

Mass stage (gross enrollment rate 15%-50%): going to college is the right of some qualified people; Teach technology and ability, and train technical and economic experts;

Popularization stage (gross enrollment rate above 50%): going to college is a social obligation of human beings; Cultivate people's social adaptability and cultivate modern social citizens.