专四语法（虚拟语气）虚拟语气用来表示说话人的主观愿望或假想，所说的是一个条件，不一定是事实，或与事实相反。
条件句可分为两类，一类为真实条件句，一类为非真实条件句。
非真实条件句表示的是假设的或实际可能性不大的情况，故采用虚拟语气。
eg. If he comes, he will bring his violin.典型例题The volleyball match will be put off if it ___.A.will rainB. rainsC. rainedD. is rained答案B。
真实条件句主句为将来时，从句用一般现在时。
注意：1）在真实条件句中，主句不能用be going to表示将来，该用shall, will. (错) If you leave now, you are never going to regret it.(对) If you leave now, you will never regret it.2）表示真理时，主句谓语动词便不用shall (will) +动词原形，而直接用一般现在时的动词形式。
从句中提出一种与客观现实不相符或根本不可能存在的条件，主句会产生的一种不可能获得的结果。
条件句中的虚拟语气根据不同的时间有三种不同的形⏹If I had time, I would do it again.⏹If I had known of your arrival, I should have met you at the station.⏹If she had further considered the problem, she might have come to the correctconclusion.真题举例：1. All of us would have enjoyed the party much more if there _____ quite such a crowd people there.（00, 49）[C]A. weren’tB. hasn’t beenC. hadn’t beenD. w ouldn’t be2. If your car _____ during the first 12 months,take it to an authorized dealer.（98, 43）[B]A. shall needB. should needC. would needD. will need3. If there were no subjunctive mood, English _____ much easier to learn.(09, 52) [B]A. could have beenB. would beC. will beD. would have been4. _____ for the fact that she broke her leg, she might have passed the exam.(02, 60）[A]A. Had it not beenB. Hadn’t it beenC. Was it notD. Were it not5. If you explained the situation to your solicitor, he _____ able to advise you much better than I can. (05, 51) [A]A. would beB. will have beenC. wasD. were6. I was to have made a speech if _____. (97, 51) [C]A. I was not called awayB. nobody would have called me awayC. I had not been called awayD. nobody called me away当条件状语从句表示的行为和主句表示的行为所发生的时间不一致时，被称为：错综时间条件句，动词的形式要根据它所表示的时间做出相应的调整。
⏹Had it not been for the timely investment from the general public, ourcompany would not be so thriving as it is.⏹(主句与现在事实相反，从句与过去事实相反)⏹Had Paul received six more votes in the last election, he would be ourchairman now.⏹(主句与现在事实相反，从句与过去事实相反)真题举例：1. Had Judy been more careful on the maths exam, she _____ much better results now. (08, 52) [D]A. would be gettingB. could have gotC. must getD. would get2. _____ if I had arrived yesterday without letting you know beforehand ?(04,54) [A]A. Would you be surprisedB. Were you surprisedC. Had you been surprisedD. Would you have been surprised⏹Your math instructor would have been happy to give you a make-upexamination had you gone and explained that your parents were ill at the time.(句子前半部分为假设情况，而“父母病了”是事实)⏹ I would have gone to visit him in the hospital had it been at all possible, but Iwas fully occupied the whole of last week.(前半部分为假设，后半部分是事实)真题举例：1. He would have finished his college education, but he _____ to quit and find ajob to support his family. （07, 60）[C]A. had hadB. hasC. hadD. would have2. _____ you ____ further problems with your printer, contact your dealer foradvice. (05, 63) [C]A. If, hadB. Have, hadC. Should, haveD. In case, had3. If your car _____ any attention during the first 12 months, take it to anauthorized dealer. (98, 43 ) [B]A. shall needB. should needC. would needD. will need有时句中并未出现条件句，其假设情况是由上下文含蓄地提供的，这种句子称为含蓄条件句。
eg. A more careful student wouldn’t have made such glaring mistakes.With his aid you would have succeeded in it.But for the rain, we should have had a pleasant journey.She must have been ill, otherwise she would have come to school.⏹(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; o therwise he wouldn’t havemade such a stupid remark.⏹I used my calculator; otherwise I’d have taken much longer.⏹(2)介词短语暗含假设条件，常用的有：without, but for, under more favorableconditions等。
如：⏹But for your timely advice, I would never have known how to go about thework.（94年）⏹The storm delayed us. But for the storm we would have been in time.⏹Supposing I accepted this offer, what would you say?⏹Without your timely help, my daughter would have drowned.⏹(3)intended/meant/hoped/wished/planned 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.真题举例：1. You ___ Jim anything about it. It was none of his business. (00, 48) [A]A. needn’t have toldB. needn’t tellC. mustn’t have toldD. mustn’t tell2. Aren't you tired? I ____ you had done enough for today. (09,61) [A]A. should have thoughtB. must have thoughtC. might have thoughtD. could have thought3. You _____ Mark anything. It was none of his business. (98, 52) [A]A. needn’t have toldB. needn’t tellC. mustn’t have toldD. mustn’t tell虚拟条件句的从句部分如果含有were, should, 或had, 可将if省略，再把were, should或had 移到从句句首，实行倒装。