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555.They ______ on the program for almost one week before I joined them,and now we ______ on it as no good results have come out so far.
A.have worked;are still working
B.had worked;were still working
C.have been working;have worked
D.had been working;are still working
556.The young girl sitting next to me on the plane was very nervous.She _______ before.
A.hasn't flown
B.didn't fly
C.hadn't flown
D.wasn't flying
