一、条件状语从句
1、表示与现在事实相反的情况:
从句:If 主语+过去时(Be动词用were)
主句:主语+should/would/could/might+do
eg:
If I were you,I would take an umbrella.
2、表示与过去事实相反的情况
从句:If 主语+had+done
主句:主语+should/would/could/might+have done
eg:
If I had got there earlier,I should/could have met her. 如果我早到那儿,我就会见到她。
3、表示对将来情况的主观推测
从句:①if+主语+were to do 主句:①主语+should/would/could/might+do
②if+主语+did/were ②主语+should/would/could/might+do
③if+主语+should+do ③主语+should/would/could/might+do
eg:
1.If he should come here tomorrow,I would talk to him.
4、 当虚拟条件句的谓语动词含有were,should,had时,if可以省略,这时条件从句要用倒装语序,即把were,should,had等词置于句首,这种多用于书面语。
eg:
Should he agree to go there,we would send him there.
二、wish 后宾语从句
a、表示与现在事实相反的愿望,谓语动词用过去式
eg. I wish I had your brains.
我希望我有你那样的头脑。(事实:我根本比不上你)
b、表示与过去事实相反的愿望,谓语动词:had+done
eg:.I wish I had known the truth of the matter.
我希望我那时就知道这件事情的真相。(事实:那时还不知道)
c、表示将来难以实现的愿望
谓语动词:should/would(情态动词) + 动词原形
eg. I wish I should have a chance again.
我希望我还能有一次这样的机会。(事实:很难再有这样的机会了)
(注:if only引导的感叹句和as if/as though引导的状语从句也有相同用法)
三、目的状语从句
1、在for fear that,in case,lest引导的从句中,若用虚拟语气时,从句谓语为:should + do。并且 should能省略
She examined the door again for fear that a thief (should) come in.
她又把门检查了一遍,以防盗贼的进入。
2、在so that,in order that所引导的目的状语从句中,从句中的谓语为:can / could / may / might / will / would / should + do。
He goes closer to the speaker so that he can hear him clearer. 他走近说话的人以便能听得更清楚。
其他用法:
1、一想要(desire一宁愿(prefer)一坚持(insist)二命令(order. command)三建议(advise. suggest. propose/recommend)四要求(demand. require. request. ask)中,无论主句谓语动词为何种时态,从句的谓语动词都用:"should + do"。should可以省略。eg:
He suggestedthat we (should) take the teacher's advice.
He insisted that we (should) take the teacher's advice.
He demand that we (should) take the teacher's advice.
He ordered that we (should) take the teacher's advice.
insist意为“坚持某种动作”才用虚拟语气;意为“坚持某种观点,某个事实”则不用虚拟语气。
eg:
He insists he is a student.
他坚持说他是个学生。
这个语句表示的是事实,因此在这个语句中不能使用虚拟语气。
suggest意为“建议”才用虚拟语气,意为“暗示”则不用虚拟语气。
eg:
His face suggests that he looks worried .
他的表情暗含着他很担心。
2、表情绪.观点的形容词或名词也要用虚拟语气.如:necessary、important、impossible、natural、strange、surprising、funny、right、wrong、better、a pity ,the shame ,no wander等。
句型:It is.......that +主语从句,从句的谓语动词都要用should+原型 或只用动词原型。
eg:
Do you think it is necessary that he (should)not be sent to Lingbao.
3、 在even if,even though 所引导的让步状语从句中用may/might+动词原形,may/might可以省略,表示与现在相反的情况;从句用过去完成时,表示与过去相反的情况,类似的词有though/even though/whatever/however/so long as; 主句、从句的结构与if所引导的条件从句结构相同。
eg:
Even if he were here himself,he should not know what to do.
即使他亲自来也不知该怎么办。(事实:他没来)
4、 在whatever,whichever,whenever,whoever,wherever,however,no matter wh-等引导的让步状语从句中,从句虚拟语气结构为:
指现在或将来:may +do。
eg:
We will finish it on time no matter what may happen.
不管发生什么事,我们都要按时完成。
5、一般would rather,had rather,would sooner等之后的宾语从句常表示与客观事实不相符的一种愿望,故使用虚拟语气。其虚拟语气的结构为:
过去 had + done
现在 过去时(be 用were )
将来 过去时(be 用were ) (would rather将来情况用一般过去时)
eg:
I'd rather you had seen the film yesterday.
我倒想你昨天看过了这场电影。
6、虚拟语气还可用在定语从句中,表示:“早该做某事了”时,定语从句中的谓语动词须用虚拟语气,其虚拟语气的结构为:It is (high / about) time that + 主语+ 动词的过去式/ should + do(优先使用动词过去式),即从句用虚拟过去式。
It is time that I went to pick up my daughter at school.
我该去学校接我的女儿了。