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...)...