题干
We ______ ; we followed the boss into the hall as his guests. How lucky we were!
A：didn’t need to wait
B：needn’t have waited
C：must have waited
D：couldn’t have waited
答案(点此获取答案解析）
A
＜
，某时刻在P点为两列波的波峰与波峰相遇，则以下叙述正确的是（ ）
