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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.

1. year toward the cost of higher education, previously paying $7 per year
2. year toward the cost of higher education, for which was previously paid $7 per year
3. year, compared to the previously $7 per year, toward the cost of higher education
4. year toward the cost of higher education, instead of the $7 per year required previously
5. year as opposed to the $7 per year required previously for the cost of higher education

Answer is D

My answer is C

貌似以前没有相关的讨论贴

Previously can only modify verb instead of noun.

c: previously $7 ( incorrect)

d: previously required( correct)