问题 选择题
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
答案

答案:A

单项选择题
单项选择题