如题所述
1、对现在情况的虚拟
条件从句中谓语动词用一般过去式,主句用“would/should/might/could+动词原形”形式,表示对现在不可能实现情况的假想。
If I were you,I would choose to work in a small town.
如果我是你,我会选择在小城镇工作。(事实上我不是你)
注意:在条件从句中,如果谓语动词是be的形式,不管主语是单数还是复数,书面语中用were,而口语中如果是单数,也可以用was,不过在if I were...中一般用were.
2、对过去情况的虚拟
条件从句中谓语动词用过去完成式,主语用“would/could/should/might+have+动词的过去分词”形式。
If it had not been for your help yesterday,I could not have caught the bus.
如果昨天没有你的帮助,我不会赶上公交车。(事实是你昨天已经帮助了我,所以我赶上了车)
3、对将来情况的虚拟
在表示与将来事实相反的条件从句中,谓语动词可用should do,were to do或动词的过去式三种形式表示,但意义略有不同。should表示的可能性最大,动词过去式的可能性次之,were to do 的可能性最小。
If things were to be twice,all would be wise.
假如凡事都可以重新做一次,人人皆可成为聪明人。(事实是并不是所有的事都可以重新做一次)
注意:在书面语中,如果虚拟条件从句中有were,had 或 should,可以把if省略,把这几个词放到主语之前,构成主谓倒装。
其他条件句:
1、错综时间条件句
有些条件句的主句谓语和从句谓语表示的动作在时间上并不一致,这类句子称为错综时间条件句。
If you had taken my advice then,you would not be in trouble now.
如果当时听我的劝,你现在就不会有麻烦了。(if 条件句是对过去的虚拟,故用过去完成时,而主句是对现在的虚拟,故用“would+动词原形”形式)
2、含蓄条件句
有些句子虽不含条件从句,但意思和条件句相差不多,这种句子称为“含蓄条件句”,这种句子有时候会用虚拟语气。
如: Without air (If there were notair), there would be no living things.
But for your help (If it ha dn'tbeen for your help) I couldn't have don e it.