2.名词性从句的虚拟形式
名词性从句是指宾语从句、主语从句、表语从句和同位语从句。从句的谓语动词需用(should+)动词原形表示虚拟。考生应熟悉：
(1)下列动词做谓语时，that宾语从句中的动词用虚拟形式：
desire, advise, recommend, command, direct, order, ask, demand, request, require, insist, maintain, move, propose, prefer, urge, vote。如：
In the past men generally preferred that their wives work in the home. I move that he be discharged for his serious mistake.
(2)下列形容词和分词做表语或补语时，that主语从句中动词用虚拟形式：
advisable, desirable, insistent, preferable, urgent, appropriate, compulsory, crucial, essential, imperative, important, necessary, obligatory, possible, probable, proper, vital, advised, arranged, commanded, demanded, desired, ordered, proposed, recommended, requested, required, suggested。如： The board deem it urgent that these files should be printed right away. It is essential that all these figures be checked twice.
(3)下列名词接同位语从句或表语从句时，从句中动词用虚拟形式：
insistence, preference, recommendation, suggestion, proposal, motion, desire, requirement, request, order, necessity, importance, regulation, rule, resolution, understanding。如：
John Wagner’s most enduring contribution to the study of Afro-American poetry is his insistence that it be analyzed in a religious, as well as worldly, frame of reference.
They keep telling us it is of utmost importance that our representative be sent to the conference on schedule.
3.含蓄虚拟条件句的谓语动词形式
含蓄虚拟语气是指假设条件不通过if从句表达，而是暗含在其他结构中。考生应熟悉：
(1)连词but, but that, or, or else;副词otherwise, unfortunately等表示转折假设。如：
A safety analysis would have identified the target as a potential danger. Unfortunately, it was never done. Victor obviously doesn’t know what’s happened; otherwise he wouldn’t have made such a stupid remark.
(2)介词短语暗含假设条件，常用的有：without, but for, under more favorable conditions等。如：
But for the English examination I would have gone to the concert last Sunday.
(3)intended/meant/hoped/wished/plann或was/were +不定式完成式或had intended/meant/planned/hoped/wished +不定式一般式暗示虚拟语气。如：
I intended to have called on you, but I was busy at that time.
(4)情态动词完成式暗示虚拟语气。如：
I should have called to make an airline reservation, but I didn’t.