结构图的主要成分有()。

It's wet on the ground. It ( )yesterday evening.must be...

未知题型It's wet on the ground. It ( )yesterday evening.
must be
B: should be
C: must have rained
D: should have rained

系统维护的类型有()。A、更正性维护B、适应性维护C、完善性维护D、预防性维护

未知题型系统维护的类型有()。

-What does this word mean, Joe? -( ).Sorry, I don't kno...

未知题型-What does this word mean, Joe? -( ).
Sorry, I don't know, either
B: Joe is a boy's name
C: Of course, I'm Joe
D: This word means Joe