题目

since 时间 ago
1.since +时间 +ago
2.since 后可以跟个时间,或是直接接句子..那是用在什么时态里面.主句要是什么时态?

提问时间：2020-10-17

答案

since的四种用法
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 two years since I became a postgraduate student.