316.In 2007 the University of Wisconsin-Madison-one of the top five or so prestigious public universities-graduated 81% of its white students within six years, but only 56% of its blacks.
在2007年，排名第五位左右的著名公立学校之一威斯康星大学麦迪逊分校，六年内白人学生的毕业率是81%，但是黑人学生的毕业率只有56%。

六级词汇讲解:

本句的主干是...the University of Wisconsin-Madison...graduated 81% of its white students..., but only 56% ofits blacks。81% ofits white students与but only后的56% ofits blacks是并列关系。one ofthe top five or so prestigious public universities是the University of Wisconsin-Madison的同位语。