大一英语作文多功能句子

(1) since句型：主句用完成时

例：My aunt has worked in a clinic since 1949.

(2) since when +完成时

例：Since when have you planted so many young trees?

从什么时候你种植了这么多小树的?

(3) This/it is the first (third...) time *** have/has done sth

This/it was the first (third...) time *** had done sth

例：This is the first time I have been here.这是***前次到这儿。

(4) by…(到……为止)到过去某个时候为止用过去完成时，到现在为止

用现在完成时，到将来某个时候为止用将来完成时。

例：She will have finished the book by my next birthday.

到我下一个生日为止，我将完成那本书。