I was supposed to wait until after....为何有两个介词？

I was supposed to wait until after....为何有两个介词？

这是“介词叠用”。有时假如语意需要，until之后可以接介词短语。又如：

The two ministers didnt close with each other until near the end of the meeting. 这两位外交使节直到会议将近结束时才达成共识。《21世纪大英汉词典》

▲until之后可以接副词、介词短语或从句。

He has been ill until recently.他近期一直生病。

She didnt return until after twelve oclock.直到12点过后她才回来。

They didnt reach the station until after the train had left. 直到火车开走之后，他们才到达车站。

Until when are you going to stay here? 你在这儿要待到什么时间？

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