We on it for several hours but we have not yet reached any conclusion.
A. work
B. areworking
C. havebeenworking
D. havebeenworked
网友回答
A. work
B. areworking
(答案→)C. havebeenworking
D. havebeenworked
解析：
答考查时态。根据but后时态，可以判断出到现在还没有得出结论，有可能还要继续下去，所以要现在完成进行时。