距离2019年12月大学英语四级考试还有不到40天时间，考生们准备得怎么样啦?文都四六级小编为大家精心准备了2019年12月英语四级语法：since的四种用法，来了解一下吧，更多四级语法、六级语法请关注文都四六级网站。

2019年12月英语四级常用语法汇总

英语四级语法：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.

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