一道英语单选问题
17.They()ontheprogramforalmostoneweekbeforeIjoinedthem,andnowwe()onitasnogoodresulthavecomeoutsofar.
A.hadbeenworking;arestillworkingB.hadworked;werestillworking
C.havebeenworking;haveworkedD.haveworked;arestillworking
答案选的是A,但我不理解为什么第一个空用过去完成进行时,而不用过去完成时