原题：
According to a 1996 survey by the National Association of College and 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.
Athan those that charge
Bthan are charging
Cthan to charge
Das charge
Eas those charging
这题如果我把划线部分改为 as those that charge 或者 as over 对不对呢，
如果是as those that charge 我认为收费低于8000刀的机构数目大于收费高于16000刀的机构的数目相比？
如果是as over, 我可以理解为把相同的内容都省略了吗