请教一道语法题

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

答案是D，这道题都怎么排除……