----You didn’t wait for Mr. Smith last night, did you?

-----Yes, but we           . He didn’t return home at all.

A．don’t have to

B．didn’t need to

C．needn’t have

D．should have

假设线性表的长度为n，则在最坏情况下，冒泡排序需要的比较次数为( )。

A．log₂n
B．n²
C．n/2
D．n(n-1) /2