1. I hadn't realized she was foreign until she spoken. 直到她讲话,我才了解到她是外国人。
为什么这句主句用过去完成时?
2. I didn't manage to do it until you had explained now.直到你解释了,我才会做。
为什么该句主句用一般过去时,从句用过去完成时?
3. He didn't leave the office until he finished his work.他完成他的工作后才离开办公室。
为什么该句主句和从句都用一般过去式?
还望老师解答一下,谢谢了!