北京大学生家教： 英语语法有成套的系统，但还是需要同学们利用零碎的时间进行逐项突破。虚拟语气：表示假设的情况与事实相反，或发生的可能性不大。

虚拟语气的常见用法和常见场景：

1. if 引导的虚拟条件句

条件从句

条件从句的谓语形式

主句的谓语形式

与过去事实相反

had +过去分词

should/would/could/might+hav done

与现在事实相反

were; did

should/would/could/might+动词原形

与将来事实相反

did; should do; were to do

should/would/could/might+动词原形  （北京大学生家教www.beishidajiajiao.com）

2.这些动词后面接的宾语从句：表示建议(suggest, advice, propose, recommend) ，要求(demand, request, require, insist), 命令(order, command)等，从句谓语用：should + 动词原形, should 可省略。 (注意：insist 表示“坚称，坚持说”，suggest 表示“表明、暗示”时, 用陈述语气，表示事实。)

　　The teacher suggested that we (should) clean the blackboard after class.

　　The smile on his face suggested that he was happy to have given his life for his country.

3. wish;as if; as thought 及if only(若是……那该多好啊)引导的从句中有三种情况：

　　1) 与现在事实相反：用过去式

　　如：I wish I were 30 years younger. 我但愿自己能年轻三十岁。

　　2) 与过去事实相反：用过去完成式（北京大学生家教www.beishidajiajiao.com）

　　如：He wished he hadn't done it. 他想要是他没这样做该多好。

　　3) 与将来事实相反：用情态动词(would / could) + do

　　如：I wish she would be on my side. 我希望她能站在我一边。

4. 在句型 “It is important (necessary, strange, natural) that .... ” that 后面从句中的谓语动词用: should + 动词原形(should不能省略)。

　　如：It is important that we should form a good habit.

　　在句型“It’s (high/right) time that…”中，谓语动词用：过去时或should + 动词原形(should不能省略)。

　　如：It is about time that we started\should start a trip.

5. 在would (had) rather(宁愿) 引导的宾语从句中, 当从句表示现在或将来的时间时,谓语动词要用一般过去时; 表示过去时间时,谓语动词要用过去完成时。

如：Mary wouldrather that she had not gone to the ball 10 years ago.

6. 一些介词短语, 如:but for(要不是), without, otherwise(否则), in that case(如果是那样的话), 表示含蓄的条件, 这时主句要用虚拟语气。

　　Without your help, we would not have made such rapid progress.