According to a 1996 survey by the National Association of College an University Business Officers, more than three times as many independent institutions of higher education charge tuition and fees of under $8,000 a year than those that charge over $16,000.
A) than those that charge
B) than are charging
C) than to charge
D) as charge
E) as those charging
答案给的是E，我觉得应该选D
D中的charge over $16,000和前面的charge tuition and fees of under $8,000 a year 对称，charge前面省略了institutions of higher education
E中的those 可能有歧义，不知道是指代institutions of higher education 还是指代tuition and fees，如果要消除歧义，把E中的charging改为charge这样those就可以明确地指代institutions of higher education
