before until since分别前后用于什么时态
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before until since分别前后用于什么时态
是否和when的用法相似
是否和when的用法相似
![before until since分别前后用于什么时态](/uploads/image/z/5317963-43-3.jpg?t=before+until+since%E5%88%86%E5%88%AB%E5%89%8D%E5%90%8E%E7%94%A8%E4%BA%8E%E4%BB%80%E4%B9%88%E6%97%B6%E6%80%81)
三个词引导时间状语从句时我区别.
before ,until 这两个词用一般现在时表示将来时.如
I will wait here until he comes back.
It will be two years before he returns.
当主句是过去时的时候从句也用过去时.如
Yesterday I waited until he came back.
He glanced at the watch before he left.
since 有它自己的用法,既它的从句用一般过去时,主句用现在完成时.
I have worked here since I came here two years ago.
before ,until 这两个词用一般现在时表示将来时.如
I will wait here until he comes back.
It will be two years before he returns.
当主句是过去时的时候从句也用过去时.如
Yesterday I waited until he came back.
He glanced at the watch before he left.
since 有它自己的用法,既它的从句用一般过去时,主句用现在完成时.
I have worked here since I came here two years ago.