问题
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;
B:had worked ;were still working
C:have been working ;have worked
D:have worked ;are still working;
正确答案是：
