Question

关于since的用法

1. It had been 2 years since he was in the army
2. It has/is been 2 years since he was in the army
3.My classmates have written to me since I lived in the city
为何第一句的翻译是参军两年而第二句是复员两年？ had been和has been 接since的意义区别是什么呢？
为何第三句的lived in the city的翻译是离开那个城市以来同学常常给我写信？而不是住在这个城市以来呢？
求解答
求解释句子，不要复制的条条框框语法点

Answer 1

since的用法有哪些

Answer 2

since的用法：译作“自从…以来”
(1)接时间点：如 I have stayed in that country since 1995.要求：谓v.用现在完成时,而且须是延续性动词.
(2)接一段时间 + ago：如 They have lived in that house since two years ago.要求：谓v.用现在完成时,而且须是延续性动词.
(3)接时间状语从句：如 I have loved her since I met her last time./ Lily has stayed at home since she left school.要求：主句的谓v.用现在完成时,而且须是延续性动词；从句的谓v.用一般过去时,而且须是终止性动词.
(4)用于句型“It’s / It has been + 一段时间 + since + 时间状语从句”中,译作“自从…以来,已经…(时间)了”.如 It’s / has been three months since he moved to this city.要求：主句的谓v.用一般现在时或现在完成时；从句的谓v.用一般过去时,而且须是终止性动词.
(5)用于句型“一段时间 + has passed since + 时间状语从句”中,译作“自从…以来,…
(时间)已经过去了”.如上个例句还可写成：Three months has passed since he moved to this city.要求：主句的谓v.用现在完成时,而且动词必须是has passed；从句的谓v.用一般过去时,而且须是终止性动词.
(6)注：当since用于否定句时,主句的谓v.可以是终止性动词.如 He hasn’t seen the film since last month.
(7)相关词组：“从那时起”：ever since、since then、from then on.
注：ever since作为一个词组,放句尾可单独使用.如I have given up smoking ever since.另外,还可在since后接句子.since前加ever,只是加重语气而已.如 I have given up smoking ever since I caught a bad cough.
(8) since还可引导原因状语从句,译作“由于；因为”,相当于because.如 Since he was lazy,he didn’t finish his homework.
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二、 一般过去时

4、 用于since引导时间状语从句中的谓语动词
1） 短暂动词的一般过去时,表示非持续性动作的结束.如：
The area has changed a great deal since I left. 自从我离开以来那地区发生了很大的变化.
It had been two years since he was in the army. 他参军两年了.
2） 持续性动词或状态动词的一般过去时,表示动作或状态的完成或结束.如：
It is / has been two years since he was in the army. 他复员两年了.
My classmates have written to me since I lived in the city. 我离开那个城市以来同学常常给我写信.

Answer 3

前两句不知道怎么解释
第三句之所以翻译成离开是因为since后面的live用了一般过去时，表示动作的完成和结束
语法参考：持续性动词或状态动词的一般过去时，表示动作或状态的完成或结束