题干
— Shall I book some seats for the concert?
—______. I've done that.
A：Yes, you may
B：No, you mustn't
C：No, you needn't
D：No, you can't
答案(点此获取答案解析）
C
— Shall I book some seats for the concert?
—______. I've done that.
A：Yes, you may
B：No, you mustn't
C：No, you needn't
D：No, you can't
、已知数列
，前
项和
，第
项满足
，则