大师作文网since 的时态及用法，谢谢合作。
来源：学生作业帮 编辑：大师作文网作业帮 分类：英语作业 时间：2024/09/21 21:45:53
解题思路： 如下
解题过程：
同学，你好！
答疑如下：
since的用法主要有两点：
一是表示“自从……以来”，（时间状语从句）
二是表示“既然”之意。（原因状语从句）
since时间状语从句的四种用法
主句用现在完成时，状语从句用一般过去时。
1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980, last month, half past six)。
I have been here since 1989.
2) since +一段时间+ ago
I have been here since five months ago.
3) since +从句
Great changes have taken place since you left.
Considerable time has elapsed since we have been here.
4) It is +一段时间+ since从句
It is / has been two years since I became a postgraduate student. 如有疑问，欢迎回复！
最终答案：略
解题过程：
同学，你好！
答疑如下：
since的用法主要有两点：
一是表示“自从……以来”，（时间状语从句）
二是表示“既然”之意。（原因状语从句）
since时间状语从句的四种用法
主句用现在完成时，状语从句用一般过去时。
1) since +过去一个时间点 (如具体的年、月、日期、钟点、1980, last month, half past six)。
I have been here since 1989.
2) since +一段时间+ ago
I have been here since five months ago.
3) since +从句
Great changes have taken place since you left.
Considerable time has elapsed since we have been here.
4) It is +一段时间+ since从句
It is / has been two years since I became a postgraduate student. 如有疑问，欢迎回复！
最终答案：略