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They ____ on the program for almost one week before I joined

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They ____ on the program for almost one week before I joined them
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.had been working; are still working B.had worked; were still working
C.have been working; have worked D.have worked; are still working
为什么?
答案错了.应该是A,before i joined them,过去的过去,用过去完成时(过去完成进行时),因为一直未完成,还在持续,所以是过去完成进行时.“我们到目前没得出结果”说明我们还在一直工作