Obviously with a total of 2,000 universities and colleges there must be great differences in quality and reputation among them. Many have achievements substantial enough for them to be well known all over the world, but among these there are a few which are outstanding in their reputation, both nationally and internationally. These include a few private institutions in various parts, and several of the greatest state universities, but none surpass the group of old private north-eastern universities commonly known as the Ivy League. Their old social-elite reputations are by now overshadowed by the reputation of their graduate schools as intellectual-elite centers. Their fees are high, but most graduate students have scholarships of some kind.
　　The best known of all is Harvard, which is situated in Cambridge, Massachusetts, in the urban area of Boston. Yale (founded in 1701) is in New Haven, between Boston and New York. There is much in common between Harvard and Yale, and together occupy a position in American university life rather like Oxford and Cambridge in England. A remarkable number of the men who hold prominent positions in public life and the big corporations were educated at one of these two. There is a certain prejudice against the kind of privilege which is associated in the public mind with these institutions, and that is not surprising in view of the American ideal of equality. For undergraduate studies, Harvard and Yale are probably somewhat more privileged, in the old (social) sense of the world, than Oxford and Cambridge in England, but they are closely followed in the preeminence by several other institutions such as Princeton (founded in 1746), now surrounded by New Jersey suburbs, and Columbia (founded in 1754) with its ugly buildings, which is close to the New York Negro quarter of Harlem. There are also many smaller institutions, mainly in the north-east, which have reputations equal to those of the Ivy League schools, but refuse to increase their numbers, believing that their small size is one of the characteristics which gives them their special quality. Some of these are liberal arts colleges, without graduates schools or courses of practical application. Most of the northeastern institutions of this kind were originally founded for men or women only, and continued as single-sex institutions into the 1960s, at least at undergraduate level. Here the 1970s have brought a major revolution, with this kind of segregation gradually eliminated. Old traditions have yielded to the pressure of new social trends.What does “old traditions” in the last sentence of the passage refer to?

A.Most of the north-eastern institutions were set up for both male and female students.

B.Most of the north-eastern institutions enrolled only men students or women students before the 1960s.

C.A lot of institutions in the north-east refused to enroll more students before the 1960s.

D.Many institutions in the north-east have the same reputation as Harvard or Yale.