问题:
The engineers must have worked out the design by the end of last week,_______?
A.mustn’t they
B.hadn’t they
C.haven’t they
D.didn’t they
The engineers must have worked out the design by the end of last week,_______?
A.mustn’t they
B.hadn’t they
C.haven’t they
D.didn’t they
A.mustn’t they
B.hadn’t they
C.haven’t they
D.didn’t they
参考答案: