虚拟语气 一、以if条件从句为虚拟语气标志 时态 从句动词形式 主句动词形式 与现在事实相反 did would/could/should/might do 与将来事实相反 (1)did (2)were to do (3)should do would/could/should/might do 与过去事实相反 had done would/could/should/might have done 注意以下两个方面： 1．含蓄条件句 有时虚拟语气并不总是用if引导的条件句来表示，而是通过一些词或短语表示出来。这些词或短语引出的条件句与if引导的条件句意义相似，如but for，with，without，otherwise，or，but等。其中but for相当于if it were not for/if it had not been for，表示“要不是……”。 He wouldn't have survived but for the neighbour's timely help.
2．在虚拟条件句中有时if是可以省略的，当if被省略后，要将从句中的were，had，should置于句首，构成倒装结构。 Were he here，he could settle the issue. 二、suggest等动词及其相应的名词后跟的从句中虚拟语气的用法 1．宾语从句 suggest等表示建议、愿望、命令等的动词后跟的宾语从句要使用虚拟语气，从句谓语的结构为“should＋动词原形”，其中should可以省略。类似用法的动词还有order，request，advise，require，insist，demand，command等。 The doctor suggested that he (should) take more rest. 2．主语从句 在“It is/was/has/had been suggested＋that引导的主语从句”中，主语从句要用虚拟语气， 即“should＋动词原形”结构，其中should可以省略。和suggest用法一样的动词还有demand，order，advise，require，propose等。 另外，在“It is/was important(necessary，desirable，advisable等)＋that引导的主语从句”中，从句也常用虚拟语气，谓语用“should＋动词原形”结构，其中should可以省略。 It is suggested that the building (should) be pulled down. It is necessary that a doctor (should) be sent for at once. 3．表语从句 当suggestion，order，proposal，demand等名词作主语时，其后的表语从句中要用虚拟语气“should＋动词原形”结构，其中should可以省略。 My advice is that you (should) give up smoking. 4．同位语从句 在suggestion，advice，order，proposal，demand等名词后跟的同位语从句中要用虚拟语气，谓语用“should＋动词原形”结构，其中should可以省略。 His suggestion that we (should) set off at 5：00 a．m.is not good enough. 三、虚拟语气的特殊句型 1．It is (high/about) time (that) sb.did sth. It is (high/about) time (that) sb.did sth.(that可以省略)表示“是某人做某事的时候了”，此句型应用虚拟语气，从句用一般过去时。另外，也可使用It is (high/about) time (that) sb.should do sth.结构，其中should不能省略。 It is 11：00 now.It is high time (that) you went/should go to bed. 2．would rather (that) sb.did sth. 当表示“宁愿某人做某事”时，如果是没有发生的动作，从句用一般过去时，即would rather sb.did sth.；如果是已经发生的动作，从句用过去完成时，即would rather sb.had done sth.。 I'd rather you left tomorrow.