GWD-TN-10的一道语法题，求解释

Christine2099

According to a 1996 survey by the National Association of College andUniversity Business Officers, more than three times as many independentinstitutions 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

答案是E
为什么不是D呢？as many institutions charge ... as (those who) charge over ...   这样不更简洁吗？

有没有高人给解释一下as...as...里省略的情况？？谢谢

Christine2099

木有人回答咩？？？

andrewyin

为什么E 的CHARGING 不和前面CHARGE 并列呢。。求解。。。
我觉得正确的是 as those charge