Question

since后面加什么时态

就像
since he____(be)here
since they_________(leave)China

Answer 1

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）。例如：
I
have
been
here
since
1989.
1989起，我一直在这儿。
2）since
+一段时间+
ago。例如：
I
have
been
here
since
five
months
ago.
我在这儿，已经有五个月了。
3）since
+从句。例如：
Great
changes
have
taken
place
since
you
left.
你走后，变化可大了。
Great
changes
have
taken
place
since
we
were
here.
我们走后，变化可大了。
4）It
is
+一段时间+
since从句。例如：
It
is
two
years
since
I
became
a
postgraduate
student.
我考上研究生有两年了。

Answer 2

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）。例如：
I
have
been
here
since
1989.
1989起，我一直在这儿。
2）since
+一段时间+
ago。例如：
I
have
been
here
since
five
months
ago.
我在这儿，已经有五个月了。
3）since
+从句。例如：
Great
changes
have
taken
place
since
you
left.
你走后，变化可大了。
Great
changes
have
taken
place
since
we
were
here.
我们走后，变化可大了。
4）It
is
+一段时间+
since从句。例如：
It
is
two
years
since
I
became
a
postgraduate
student.
我考上研究生有两年了。

Answer 3

一、since通常通常搭配的时态　　
当since表示“自从”时，不管它是用作介词、连词还是副词，它通常都要与现在完成时连用。　　
I’ve worn glasses since my childhood. 我从小就戴眼镜。　　
The works have been closed since January. 一月份以来这些厂就关闭了。　　
He’s put on a lot of weight since he gave up smoking. 他戒烟后体重增加了许多。　　
Nothing has happened since. 从那以后未发生什么事。　　
She moved to London last May and has since got a job on a newspaper. 她去年五月到伦敦 此后一直在报社工作。　　
有时连用现在完成进行时。如：　　
He has been working since noon. 他从中午就开始工作了。　　

二、since搭配时态的特殊情况　　
虽然since通常要与现在完成时连用，但在以下情况，它也可以连用除完成时态以外的其他时态：1. 当主句表示“多长时间”时，动词可用一般现在时（当然也可用现在完成时）。如：　　
It’s a long time since I met you last. 好久不见了。　　
It’s just a week since we arrived here. 我们到这里才一个星期。　　
It’s a long time since I met you last. 从上次见到你，已有很长时间了。　　
以上各句的it is也可换成 it has been，不过在口语或非正式文体中，用一般现在时的情形比较普遍。　　
2. 当主句谓语动词为seem等连系动词时。如：　　
It seems like years since we last met. 我们似乎几年未见面了。　　
It seems like years since I last saw you. 从上次见到你以来好像已经有许多年了。　　
3. 当主句和从句表示情况“变化”时。如：　　
She doesn’t come round to see us so much since her marriage. 自从结了婚，她不怎么过来看我们了。（原来经常来，结婚后就不怎么来了）　　
Since he went on that course he thinks he knows everything. 自从他选了那门课程，他就认为自己什么都懂了。（原来不认为自己什么都懂，但选了那门课程后就认为自己什么都懂了）
since he_was___(be)here自从他来到这。
since they_____left____(leave)China自从他离开中国。