专四考试中有两项都会用到语法，一个是完型填空，一个是语言知识题，其中，语言知识的语法比重占据了很大一部分，因此掌握语法是过专四的一门必修课。

考点1. If从句中的虚拟语气
省略if，从句的语序用到装，即将were,had或 should移至主语的前面，但否定词not不前移。

一、与过去事实相反：从句sb had done，主句sb would(should,could,might)+ have done；
1. Had Judy been more careful on the maths exam, she _could have got___ much better results now.2008
  A. would be getting B. could have got C. must get D. would get
2. He would have finished his college education, but he _had___to quit and find a job to support his family.2007
  A. had had B. has C. had D. would have
3._Had he not been taken good care of __, he would not have recovered so quickly.2005/1995
  A. Hadn't he been taken good care of B. Had he not been taken good care of
  C. Had not he been taken good care of D. Had he been not taken good care of
4. I _would have enjoyed__the party much more if there hadn’t been quite such a crowd of people there.2004/1996
  A. would enjoy B. will have enjoyed C. would have enjoyed D. will be enjoying
5. All of us would have enjoyed the party much more if there _had not been__ quite such a crowd of people there.2004/2000
  A. weren’t B. hasn’t been C. hadn’t been D. wouldn’t
6. _Had it not been__for the fact that she broke her leg, she might have passed the exam.2002
  A. Had it not been B. Hadn’t it been C. Was it not D. Were it not
7. _Given____enough time and money, the researchers would have been able to discover more in this field.1998
a. Giving b. To give c. Given d. Being given
8. I was to have made a speech if_I had not been called away__.1997
A. I was not called away B. nobody would have called me away
C. I had not been called away D. nobody called me away
9. __Given___ time, he’ll make a first-class tennis player. 1996
A. Having B. Given C. Giving D. Had
10. We could _have provided__him with a detached house when he came, but he had specifically asked for a small flat.1995
A. provide B. have provided C. not provide D. not have provided
11. _Had I realized_____you were busy, I wouldn’t have bothered you with my questions. 1994
A. If I realized B. Had I realized C. I realized that D. As I realized
12. _Had it not been for____ their help, we would not have succeeded.1992
A. Hadn't been for B. Had it not been for C. It hadn't been for D. Had not it been for
13. If you _had not been____ in such a hurry you would not have put sugar into the sauce instead of salt.1992
A. were not, would not put B. were, would put
C. had been, would have put D. had not been, would not have put
14. "Did you hear of his death?'
"Yes. If he _had been operated on__ in time, hemight not have died___.”1990
A. had been operated on, might not die B. had been operated on, might not have died
C. were operated on, might not die D. were operated on,- might not have died

二、 与现在事实相反：从句sb did(were)，主句sb would(should, could, might)+do；
1. If there were no subjunctive mood, English _would be____ much easier to learn.2009
A. could have been B. would be C. will be D. would have been
2. “You _could_____ borrow my notes provided you take care of them,” I told my friend. 2007
A. could B. should C. must D. can正确答案是陈述语序
3. If you explained the situation to your solicitor, he _would be_______ able to advise you much better than I can.2005
A. would be B. will have been C. was D. Were
4. If I knew Japanese , I _would apply_____ for the position.1991
A. would apply B. will apply C. may have applied D. will have applied
三、与将来事实相反：从句sb did (should+do或were+to do)，主句sb would (should, could, might)+do。
1. _Should ____ you _have____ further problems with your printer, contact your dealer for advice.2005
A. If, had B. Have, had C. Should, have D. In case, had
2. This is an illness that can result in total blindness _if ______left untreated.2000
A. after B. if C. since D. unless
3. If your car would need____ any attention during the first 12 months, take it to an authorized dealer. (1998)
A. shall need B. should need C. would need D. will need
4、错综条件句，也就是主句与从句的动作发生在不同的时间段。根据历年真题能看出，一般以考察从句对过去虚拟，而主句对现在虚拟为主，即从句sb had done，主句sb would(should, could, might)+do；
1. If only the patient _had received_____ a different treatment instead of using the antibiotics, he might still be alive now.2007
A. had received B. received C. should receive D. were receiving
2._Would you be surprised___ if I had arrived yesterday without letting you know beforehand?2004
A. Would you be surprised B. Were you surprised
C. Had you been surprised D. Would you have been surprised

考点2：表示建议、要求、命令等动词如insist, order, command, suggest, advise, propose, ask, require, request, demand引导的从句及it引导的相应的分词、名词和形容词从句，谓语用（should)+动词原形。
1. It was recommended that passengers _not __ smoke during the flight.(2004/1994)
A. not B. need not C. could not D. would not
2. He left orders that nothing _should be_____touched until the police arrived here.1997
A. should be B. ought to be C. must be D. would be
3. She asked that she __be____ allowed to see her son in police custody. 1993
be be
4. The teacher demanded _that Tom hand in_____ his essay immediately.1991
A. Tom to hand in B. that Tom hands in C. that Tom handed in D. that Tom hand in 

考点3：It is +advisable, essential, important, imperative, incredible等从句，谓语用（should）+动词原形。
1. It is necessary that he _hand in___ the assignment without delay.2010
A. hand in B. hands in C. must hand in D. has to hand in
2. It is absolutely essential that William _continue___ his study in spite of some learning difficulties.2007
A. will continue B. continued C. continue D. continues
3. It is imperative that the government _attract_ more investment into the shipbuilding industry.2006
A. attracts B. shall attract C. attract D. has to
4.It is imperative that students _hand in___ their term papers on time.2004
A. hand in B. would hand in C. have to hand in D. handed in
5. The opening ceremony is a great occasion. It is essential _for us to be prepared____for that.2003
A. for us to be prepared B. that we are prepared C. of us to be prepared D. our being prepared

考点4：it is (high/about) time that的结构中，从句使用一般过去式。例如:
1. It’s high time we _stopped_ cutting down the rainforests.2006
A stopped B had to stop C shall stop D stop
2. That was not the first time he _had betrayed_______ us. I think it’s high time we __took______ strong actions against him2005.
A. betrayed…take B. had betrayed…took C. has betrayed…took D. has betrayed…take
3. “What courses are you going to do next semester?”
“I don’t know. But it’s about time _i decided_____on something.” 2002
A. I’d decide B. I decided C. I decide D. I’m deciding
4. If you have really been studying English for so long, it’s about time you _were__able to write letters in English.1999
A. should be B. were C. must be D. are

考点5：much as"尽管，虽然"引导让步状语从句，从句中用would have done表示假设。
1. Much as _i would have liked to___, I couldn’t lend him the money because I simply didn’t have that much spare cash.1999
A.I would have liked to B.I would like to have C.I should have to like D.I should have liked to

考点6：if only, wish, as if/as though引导从句，与过去事实相反：had + done；与现在事实相反：动词过去式；与将来事实相反：could/would + do。
1. If only I _could _play the guitar as well as you! 2006
A would B could C should D might

考点7：would rather/sooner从句中使用一般过去式或过去完成式分别表示对现在或过去的虚拟。
1. The manager would rather his daughter did not work____ in the same office now.
not worked to work not work not work

考点8：On condition that...“只有”“条件是”/lest / for fear that+(should ) +原形动词。
1. He asked me to lend him some money, which I agreed to do, _on condition_______ that he (should) pay me back the following week.2005
A. on occasion B. on purpose C. on condition D. only if

考点9：but for 要不是。。。。就不能。。。
1. _But for____ your timely advice, I would never have known how to go about the work.1994
A. Unless B. But for C. Except for D. Not for

考点10：其它
1. We consider _it strange that _____ he should have left without telling anyone beforehand. 2009
A. strange why B. it strange what C. it strange that D. that strange
2. _Be he rich or poor___, I’ll marry him all the same.2004
A. Was he rich or poor B. Whether rich or poor C. Were he rich or poor D. Be he rich or poor
3. Whether my brother be right or wrong, he will have my unwavering support.2001
A. Is B. Were C. Be D. Would be
4. Home is home, _be it____ ever so homely.1992
A. it is B. it were C. be it D. it be