1.主從句謂語動詞的時態(tài)
(1)掌握主從句謂語動詞的規(guī)范搭配:
主句
從句
與現(xiàn)在事實相反
would/情態(tài)動詞過去式+do
were (不分人稱)/did
與過去事實相反
would/情態(tài)動詞過去式+have done
had done
與將來事實相反
would/情態(tài)動詞過去式+do
should do / were to do
如：If the doctor had been available, the child could not have died.
There is a real possibility that these animals could be frightened, should there be a sudden loud noise.
(2)區(qū)分主從句表示的不同時間概念：
主從句謂語動詞所指時間不同，這叫做錯綜時間條件句，動詞形式應(yīng)根據(jù)實際情況來調(diào)整。如：
Had it not been for the timely investment from the general public, our company would not be so thriving as it is.
(主句與現(xiàn)在事實相反，從句與過去事實相反)
Had Paul received six more votes in the last election, he would be our chairman now.
(主句與現(xiàn)在事實相反，從句與過去事實相反)
(3)識別事實和假設(shè)混合句：
Your math instructor would have been happy to give you a make-up examination had you gone and explained that your parents were ill at the time.
(句子前半部分為假設(shè)情況，而“父母病了”是事實)
I would have gone to visit him in the hospital had it been at all possible, but I was fully occupied the whole of last week.
(前半部分為假設(shè)，后半部分是事實)
2.名詞性從句的虛擬形式
名詞性從句是指賓語從句、主語從句、表語從句和同位語從句。從句的謂語動詞需用(should+)動詞原形表示虛擬。考生應(yīng)熟悉：
(1)下列動詞做謂語時，that賓語從句中的動詞用虛擬形式：
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)下列形容詞和分詞做表語或補語時，that主語從句中動詞用虛擬形式：
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)下列名詞接同位語從句或表語從句時，從句中動詞用虛擬形式：
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.
