in vain __________ to persuade her to give up her wrong opinion and cooperate with us
问题描述：
in vain __________ to persuade her to give up her wrong opinion and cooperate with us
A.we tried B.we had tried C.did we try D.had we tried 为什么?
答
in vain 表示否定意思,放在句首要部分倒装,就是说把助动词（或情态动词）提到主语前面,原句应该是一般过去时,所以用did放在we前面,后面动词原形,类似的还有no,seldom,hardly等这些表示否定的词放句首也部分倒装