GWD 18的一道语法题 困惑了好久好久

Most of Portugal’s 250,000 university students boycotted classes in a one-day strike to protest a law that requires them to contribute $330 a
            year toward the cost of higher education, previously paying $7 per year.

A.    year toward the cost of higher education, previously paying $7 per year

B.    year toward the cost of higher education, for which was previously paid $7 per year

C.    year, compared to the previously $7 per year, toward the cost of higher education

D.    year toward the cost of higher education, instead of the $7 per year required previously

E.     year as opposed to the $7 per year required previously for the cost of higher education

这题的答案是D 我选的是C  C中compared to the previously $7 per year 作为插入语不好吗？？？？  跪求牛牛们呀！！！！！！！！！！！！！！！

而且我上网查了 compared to 是强调同类事物；compared with是强调就有共同点又有不一样 所以这里应该不是compared to 的问题啊！！！！

我想这是一个方面吧，也许instead of比compare with用在这里逻辑意思更通