题干
Come on, baby. We have already done _________ of the work.
A：two-three
B：two-third
C：two-thirds
D：second-three
答案(点此获取答案解析）
C
Come on, baby. We have already done _________ of the work.
A：two-three
B：two-third
C：two-thirds
D：second-three
的前
项和为
，若
，
，则
