高等继续教育 / 专科英语I
正确率：100%
题型描述: 单选题
Each year we waste tons of paper, and _ _ _ _ _ _ for many years.
A. did so
B. does so
C. had done so
D. have done so
Each year we waste tons of paper, and _ _ _ _ _ _ for many years.
A. did so
B. does so
C. had done so
D. have done so
参考答案：