虚拟语气

1. 对现在和将来的虚拟: 主句用 would + do, 从句用一般过去时
   If you are a tear in my eyes, I will never shed it.
   If you were a tear in my eyes, I would never shed it.

2. 对过去的虚拟: 主句用 could + have done, 从句用过去完成时
   If I was a dog, I could sleep with you.
   If I had been a dog, I could have slept beside you.

3. 注意
   (1) 虚拟语气中, 所有 be 动词的过去式只有 were, 没有 was
   (2) would=could=might

1. 以下情况, 从句用 "should + v"表示虚拟, 并且 should 可以省略
   (1) 以防: in case that, for fear that, lest
   (2) 命: order, direct, command
   (3) 贱: suggest, advise, propose
   (4) 要求: ask, request, require, demand
   (5) 用虚拟
   (6) 是必要的: It is necessary/important/urgent that...

2. 一下情况, 从句用过去时表示虚拟
   (1) would rather(宁愿)
       I would rather that you were happier than I.
   (2) It is high time that
       It is high time that we poured attention into the issue and took necessary actions.

3. 一下情况要区别对待: 把它本来的时态往后推成它的过去式
   (1) wish, if only(如果...那该多好啊)
   (2) but for(要不是), or/otherwise(否则)
   (3) as if/as though(好像)

1. 完形填空: 只要在句子中见到, would/could/might/过去完成时, 逻辑关系词一般选 if
2. 长难句分析: 虚拟或者不虚拟, 翻译出来中文意思完全相同