1. 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 此题的时间参照点是before I joined them,,所以第一个空应该用过去完成进行时,第二个空根据时间now用现在进行时。
2. It would be a good idea to use a plastic bottle, ___cut off, as a container to grow young plants in. A. of which the top B. the top is C. the top of which D. with its top
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