297.It is not rare in _______ that people in _____ fifties are going to university for further education.
A.1990s;the
B.the 1990s;/
C.1990s;their
D.the 1990s;their
298.Every few _____ along the Great Wall there are some watch towers.
A.hundred metres
B.hundreds metre
C.hundreds of metre
D.hundred of metres
297.答案是D；表示几十年代时用定冠词the+年代的复数；表示几十多岁时，用one's + 几十的复数。
298.答案是A;hundred,thousand,million等词被数词修饰时用单数。
