(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 sb have/has done sth
This/it was the first (third...) time sb had done sth
例：This is the first time I have been here.这是我第一次到这儿。
(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。
大一英语作文万能句子 扩展
Dear Nancy,Thanks for your letter. I’m glad to hear that you are going to travel to Wenzhou. Now I’d like to tell you something about Wenzhou.
Wenzhou is in eastern China,and it is a beautiful city where the people are really friendly. There are many famous sights here,such as Yandang Mountains and Nanji Island.
