It is 3 years since he joined the army.为什么用is不用has been

问题描述:

It is 3 years since he joined the army.为什么用is不用has been
1个回答 分类:英语 2014-11-21

问题解答:

我来补答
since是现在完成时的标志,但是since+过去的时间点或是过去时态从句,下面的例句是摘抄的,你参考下.我觉的,两个应该都行,你说的应该也是对的.因为joined 也是瞬时动词.
It is / has been + 一段时间 +since 从句.例如:
  It is / has been three years since we saw each other last time.
  我们上一次见面是在 3 年前.
  It is four years since I became a student.
  我上了 4 年学了.
  (注意:状语从句中常用短暂性动词的一般过去时作谓语动词)
  注意:since 从句里的谓语动词是瞬间动词时,表示这段时间从该动作开始时算起; since 从句里的谓语动词是延续性 / 表状态的动词时,则表示这段时间从动作结束时算起.例如:
  It's five years since he lived here.
  他离开这儿有 5 年了.( live 为延续性动词)
  It's ten years since he joined the army.
  他参军已有 10 年了.( join 为瞬间动词)
 
 
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