这道英语题怎么做We ______ out by that time that he _____ a spy for a
3个回答

这句话的意思是“到那个时候我们已经知道他已经做间谍很久了”.

by that time完成时态的标志性时间状语,for a long time 同理.而且你的答案写错了,A应该是 had found; had been (不是seen吧)

这句话还可以写成 By that time we had found that he had been a spy for a long time.