虚拟语气
有些条件句是可能实现的，称为真实条件句. 虚拟语气是动词的一种特殊形式，用来表达说话人的意愿.请求，设想，等未能或不可能实现的事实，或说话人看来实现可能性很小的情况.做这类题时首先要弄清楚虚拟语气的各种句型，即由if引导的虚拟条件句，省略if的倒装形式，可跟虚拟语气的宾语从句，同位语从句，表语从句的句型，以及表示祝愿或感叹的句子和由without， but for等介词引导的短语或句子.
主要用法
1). 主语从句，同位语从句中虚拟语气的用法.
2). 宾语从句中虚拟语气的用法，尤其是wish 虚拟语气结构的用法.
3). If条件句中虚拟语气的用法，应特别注意省略if的倒装结构是考试的重点.
4). would rather（=wish）等结构中虚拟语气的用法.
5). if only（如果。。。就好了）结构中虚拟语气的用法.
6). But， or， otherwise 等含蓄条件句的用法.
7). It’s time (that)（早该。。。。）等结构中虚拟语气的用法.
1. 虚拟语气在虚拟条件句中的运用
(1) 虚拟语气现在时，用以表示与现在/将来事实相反的假设或现在实
现可能性不大的情况.
Eg. If I were a bird， I would fly to you.
If it is not for their help， we shall be in a very difficult position.
If it were not for their help， we should be in a very difficult position.
If I had seen the film, I would…..
(2) 虚拟语气过去式. 表示与过去事实完全相反的假设.
Eg. If we had started earlier， we should not have missed the train.
If she hadn’t been ill， she might have come.
If she were not ill， she might come.
◆书面语中，如果从句里含有should， had， were或其他助动词，则
可将从属连词if省去，将助动词.情态动词.be或have放在句首形成部分倒装.
Eg.Were he in your position，he’d do the same.
If he Were in your position，he’d do the same.
Had I had time， I would have done that yesterday.
If I Had had time， I would have done that yesterday.
If he Should (万一)come tomorrow， I should give him the dictionary.
(3) 虚拟语气在某些从句中的应用.
A)在(表现了说话人的愿望)wish， suggest， order， demand， propose，
command， request， recommend， require， decide， insist， desire，urge等动词的宾语从句(should:应该) + 动词原形.
以及would rather /sooner that后要用“ (should:应该) + 动词原形” 来表示愿望，建议，命令，要求等;
由上述动词派生或转化的名词suggestion， proposal， plan，motion， recommendation， demand， order， desire， request，
requirement， insistence， advice， decision ， obligatory(义不容辞的，必须的同位语从句或表语从句中也要用相应的虚拟形式.
Eg. His suggestion was that we (should) go at once.
Wang insisted that we go at once.
B)在It is/was + 某些形容词 + that (表现了说话人的愿望)从句的句
型中，that从句中的谓语动词常用虚拟语气，即“should + 动词原形”
这些形容词有:
important， necessary， essential， imperative， natural， strange，advisable， desirable， possible， probable， astonishing，
surprising， desired， suggested， requested， recommended，
ordered， proposed， decided， moved等.
C) “ should(居然/竟然) + 动词原形(或完成形式)” 可表示惊奇，遗憾，怀疑，不满等.
ⅰ. 用于expect， believe， think， suspect 等动词的否定或疑问形式后的宾语从句中.
Eg. I never expected that the new apartment should be so small.
ⅱ. 用于“It is a pity， it is a shame， it is no wonder 等+ that”
等结构后的主语从句中.
Eg. It is a pity that he should be so careless.
D) 在由for fear that， in case， lest 等引导的状语从句中，用
“ should (万一)+ 动词原形” 表示“惟恐”的意思.
Eg. He handled the instrument with care for fear that it should be damaged.
