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2016卫生职称英语考试句型：

By the time+从句，＋主句（注意时态的变化。）

如：

By the time you came back,I had finished this book.到你回来时，我已经写完了这本书。

By the time you come back,I will have finished this book.到你回来时，我将写完这本书了。