虛擬語氣是動(dòng)詞的一種特殊形式，用來表達(dá)說話人的愿望、請(qǐng)求、意圖、建議、驚奇、設(shè)想等。虛擬語氣在各種結(jié)構(gòu)中的運(yùn)用是歷年三級(jí)統(tǒng)考必考的內(nèi)容，考生必須熟練掌握。以下從五個(gè)方面介紹。
一、虛擬條件句中虛擬語氣的運(yùn)用：
虛擬條件句從時(shí)間上又分為與現(xiàn)在事實(shí)相反，與過去事實(shí)相反，與將來事實(shí)可能相反三種情況。表示與現(xiàn)在事實(shí)相反的，if從句用過去式，主句用would （或could ,should ,might）加原形動(dòng)詞。與過去事實(shí)相反的，if從句用過去完成時(shí)，主句用would（或could ,should ,might）+have done結(jié)構(gòu)。與將來事實(shí)可能相反的，if 從句用should （或were to ）加動(dòng)詞原形，主句用would加動(dòng)詞原形。
1、If a better material _____, the strength of the part would have been increased.
A. had been used
B. had been using
C. being used
D. using
�。ǜ鶕�(jù)前面的講解，正確答案為A。） （1992年58題）
2、Had the weather been good, the children _____ out for a walk.
A. had gone
B. could have gone
C. would go
D. went
�。ù鸢福築。與過去的事實(shí)相反。當(dāng)if從句中含有were, had, should這三個(gè)詞時(shí)，if可以省略，主謂倒裝。）（2001年57題）
二、某些動(dòng)詞后的賓語從句以及某些名詞后的表語或同位語從句中虛擬語氣的運(yùn)用，這些動(dòng)詞或名詞包括：
suggest （suggestion）,propose（proposal）,advise （advice）demand, insist, order, request, require, recommend, desire, ask, decide等。在這些從句中，謂語形式為should加動(dòng)詞原形，should可以省略。
例：The general’s command was that the soldiers _____ their fort and carry out more important task.
A. would leave
B. leave
C. left
D. have left
�。ù鸢福築） （2002年49題）
三、在It is desired （或desirable）, It is important等結(jié)構(gòu)后面的主語從句中，動(dòng)詞用原形或should+原形動(dòng)詞。這些結(jié)構(gòu)有：
“It is suggested”, “It is requested”,“It was ordered”, “It is necessary”, “It is essential”, “It is vital”, “It is urgent”,“ It is impossible”, “It is preferable”, “It is advisable”, “It was proposed”等。
例：It’s desired that she _____ to teach us at least twice a week.
A. comes
B. will com
C. come
D. may come
（答案：C）（1997年29題）
四、would rather, as if/though 以及wish后邊that從句中虛擬語氣的運(yùn)用。
1、I am too busy these days. I would rather all of you _____ next month for a dinner.
A. come
B. would come
C. came
D. have come
（答案：C。would rather 高中學(xué)習(xí)方法 后面的從句中，動(dòng)詞用過去式。）（2002年46題）
2、He talks as if he _____ everything in the world.
A. knows
B. knew
C. had known
D. would have know
�。ㄕ_答案為B。在as if/though后邊的方式狀語從句中，表示與現(xiàn)在事實(shí)相反或?qū)ΜF(xiàn)在的情況有所懷疑，動(dòng)詞用過去式；如果表示的是中的過去的動(dòng)作，用過去完成時(shí)。本句表示對(duì)現(xiàn)在的情況有所懷疑。）（1998年45題）
3、You look as if you had seen a ghost.
�。ù司渲衋s if 后邊是說話人想象中的動(dòng)作，所以用過去完成時(shí)。）
4、I wish I knew his address.
�。ㄔ趙ish后邊的從句中，如果指現(xiàn)在或?qū)淼脑竿�，�?dòng)詞用過去式。這句話告訴我們說話人并不知道他的地址。）
5、Peter wishes that he _____ law instead of literature when he was in college。
A. could study
B. studied
C. had studied
D. would study
�。ù鸢笧镃。表示過去沒有實(shí)現(xiàn)的愿望，動(dòng)詞用過去完成時(shí)。）（2000年32題）
五、在It is （high） time后邊的that從句中，動(dòng)詞用過去式，表示該做某事了。
例：Don’t you think it is time you _____ smoking?
A. give up
B. gave up
C. would give up
D. should give up
（答案為B。）（1999年31題）
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