求问语法问题，一个啊！！！

LQH

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.

• Ayear toward the cost of higher education, previously paying $7 per year  分析A选项
• Byear toward the cost of higher education, for which was previously paid $7 per year  分析B选项
• Cyear, compared to the previously $7 per year, toward the cost of higher education  分析C选项
• Dyear toward the cost of higher education, instead of the $7 per year required previously  分析D选项
• Eyear as opposed to the $7 per year required previously for the cost of higher education  分析E选项
  

无论如何都不明白B的问题！！！！还麻烦请解释一下C
答案选D