if的3种假设。。

造句 3个。。 以及 would 在什么情况下后面要+be

一、概念

[Subjunctive Mood]
中文译作"虚拟语气"。它是一种动词形式，表示说话人的某种假设、愿望、怀疑、猜测、建议等含义。


二、语法结构
1.if结构（非真实条件句——表示的是假设的或实际可能性不大的情况）

与..事实相反 If从句 主句
过去 Had done Would* have done
现在 Were/did Would* do
将来 Should do/were/were to do Would* do

例句：If there hadn’t been much rain in spring, we would have had a good harvest now. [过去]
If he smoked less, his cough might be well soon. [现在]
If the lecturer should be late, you would have to make a speech first. [将来]

备注：
（1）上表中’*’，would都可转换为should、could、might。
（2) 如果为时间错综句的话，左右两栏可互相搭配，排列组合。
例句：
He would still be alive today if he hadn’t taken that drug.
[与现在事实相反] [与过去事实相反]

(3) if可转换为其他形式
例句：Without your advice, our meeting wouldn’t have been so successfully. [过去]
（=>可转换为：If there hadn’t been your advice, we …）
Your notes are almost illegible (难以辨认的). Notes typed out would be a lot easier to read. [将来]
(=> 可转换为：If the notes had been typed out, it would be a lot easier to read.)
I should have gone to see Dr. Smith and he might have cured me of the disease.[过去]
(=> 可转换为：If he have gone to see Dr. Smith, he ..)