题目内容：

--you can't answer this questions,we have to ask someone for help.A.since
--you can't answer this questions,we have to ask someone for help.A.Although .B.While.C.Whether.D.Since

优质解答

D（既然你回答不出这个问题,我们只好求助其他人了）
since 既然;因为,由于,如；
He must have taken the book since it isn't here.
他一定是把书拿走了,因为书已不在这里了.
Since it is so hot,let's go swimming.
既然天气这么热,我们去游泳吧.