It is such colleges, thriving but threatened, that I worry about. Low enrollment is not their chief problem. Even with full enrollments, they may go under. Efforts to save them, and preferably to keep them private, are a national necessity. (79) There is no basis. for arguing that private schools are bound to be better than public schools. There are plentiful examples to the contrary. Anyone can name state universities and colleges that rank as the finest in the nation and the world. It is now inevitable that public institutions will be dominant, and therefore diversity (多样性) is a national necessity. Diversity in the way we support schools tends to give us a healthy diversity in the forms of education. In ah imperfect society such as ours, uniformity of education throughout the nation could be dangerous, ha an imperfect society, diversity is a positive good. Eager supporters of public higher education know the importance of keeping private higher education healthy.
第6题：In the passage, the author asks the public to support_____ .

A. private higher education in general
B. public higher education in general
C. high-quality private universities and colleges
D. high-quality state universities and colleges