题目

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：A 解析: 略 _______的完成，我国开始改变工业落后的面貌。