语法

• 过去进行时

  was/were doing

• 将来进行时

  shall/will be doing
  1、将来某一时间或某一段时间正在进行的动作
  2、不久就要发生，或一定要发生的动作
  3、询问、有礼貌的询问，比一般将来更礼貌
  4、我估计，我猜测

• 现在完成时

  have/has done
  1、动作发生在过去，对现在有影响
  2、动作发生在过去，持续到现在
  3、as soon as、after、before、till/until、when、if 等状语从句中，常用现完表示将来完成的动作。
  4、句中出现 so fa、up to now、up to present、these days，需要用现完。
  5、It is the first/second/third … time that、It is the only、It is the best/worst/most interesting…、It is…since…that，从句中的谓语动词必须是现完。
  总结：当出现了 yet，肯定要用现完。

• 过去完成时

  had done
  过去的过去用过完
  1、by、before，一个动作在另一个动作前已经完成
  2、no sooner+过完+than+一过【一…就…】、hardly+过完+when+一过【还没来得及…就…】
  3、常表过去的将来
  4、用于虚拟语气条件句中标识与过去事实相反。
  
  5、hope、expect、think、intend、mean、want、suppose、plan等用过完标识未实现的愿望、打算和意图。

• 现在完成进行时

  have/has been doing
  强调动作的长久
  1、和时间状语连用：for hours, since this morning 等
  2、动作刚刚停止
  3、某种感情色彩
  4、某种企图和尝试(不常用)
  Note：一般不适用于状态动词 hope、want

• 过去完成进行时

  had been doing
  She asked me what I had been doing these years.
  They were sweating all over because they had been playing basketball.

• 将来完成时

  will have done
  We will have finished our course be the end of the year.

现在完成和一般过去的区别

He has joined the amy for four years. ❌ join 是短暂动作
He has stayed the amy for four years. ✅
He joined the amy for four years. ✅