英语六级语法冲刺之特定句型

英语自学网

since和for的用法：
　　since 用来说明动作起始时间，for用来说明动作延续时间长度;
　　eg：I have lived here for more than twenty years.
　　I have lived here since I was born.
　　for后面多接一段时间，而since后面则接一个时间点，若since后面也出现时间段，则在时间段后加ago;
　　eg： I have lived here for twenty years ago.
　　错句：I have worked here since twenty years.
　　since句型：
　　It is +一段时间+ since从句，since从句要用一般过去时;
        　　eg：It is two years since I became a postgraduate student.