最基本的虚拟语气句型:1. 虚拟现在时表示与现在事实相反的假设，其if 从句的谓语形式用动词的过去式be 一般用were，主句用would should could might +动词原形。If places were alike, there would be little need for geographers.如果各个地方都一样，就不需要地理学家了。2. 虚拟过去时是表示与过去事实相反的假设，if 从句的谓语形式用过去完成时即had＋过去分词，主句用would should could might + have +过去分词。If he had known your address yesterday,he would have telephoned you.3. 虚拟将来时是表示对将来实现的可能性很小的或不确定的假设。If从句的谓语形式用一般过去式或用were to should +动词原形，主句用would shouldcould might +动词原形。If he were to leave today, he would get there by Friday4. 省略if 采用倒装语序的条件句。有时可以把含有助动词、情态动词、be或have的虚拟条件句中的连词if省去，而将had , should, were 等词提到主语之前，即用倒装结构。If he had worked harder, he would have got through the exams.==Had he worked harder, he would have got through the exams.If he were to leave today, he would get there by Friday.==Were he to leave today, he would get there by Friday.If I were in your place, I wouldnt do that.==Were I in your place, I wouldnt do that.5. 有时虚拟条件句并没用if 从句表示出来，而是用介词短语otherwise, or, without, but for、上下文或其它方式来表示。如 We didn't know his telephone number; otherwise we would have telephoned him. Without you help, I wouldnt have achieved so much. But for 要不是......的意思your help, I would not have succeeded.二: 虚拟语气在从句中用should的情况:1. 在表示建议,要求,命令,想法的动词后的从句里, 用should + 动词原形, should 可以省略. 如 advise, agree, command, decide, demand, determine, grant, indicate, insist, order, prefer, propose, request, require, stipulate, suggest, urge, vote.常考到的是: suggest, advise, demand, require, propose, insist, order, request.His doctor suggested that he should take short leave of absence.The author proposed that TV should be turned off at least one hour every day.2. 在表示建议,要求,命令,想法的名词后的从句里, 用should + 动词原形, should可以省略. 如 advice, decision,agreement, command, decree, demand, determination, indication, insistence, order, preference, proposal, request, requirement, stipulation etc.It was Bills suggestion that everyone should have a map.His suggestion was that everyone should have a map.He gave us a suggestion that everyone should have a map.3. 在It iswas +形容词后的that 从句中用should的结构, should 可以省略. 这类形容词常见的有: advisable, anxious, compulsory, crucial, desirable, eager, essential, fitting, imperative绝对必要, impossible, improper, important, natural, necessary, obligatory, possible, preferable, probable, recommended, urgent, vital etc.Its natural that she should do so.It is essential that we should tell her the news.4. 在 lest 和 for fear that以免,in case以防从句中用should, should 可以省略.She walked quietly lest she should wake up her roommates.Have your gun ready in case we should need it.三: wish 后的 that 从句中:1. 表示现在或将来的愿望,从句中过去式.I wish I knew his address.I wish I were young.2. 表示过去没有实现或不可能实现的愿望, 从句用过去完成式或would, could, might + have + 过去分词.I wish you had written to him.I wish I could have slept longer this morning, but I had to get up and come to class.3. 如果将wish改成wished, 其后that 从句中动词的形式不变.4. 如果that 从句中用would , 一般表示 对现状不满或希望未来有所改变或请求I wish he would answer my letter.I wish prices would come down.I wish you would help me.I wish you would stop asking silly questions.四: 在 Its about high firstsecond, third etctime 后的that 从句中,用过去式.表示该是做什么的时候了It is about time you were in bed.It is high time we left.It is the first time I came here.五: 在would rather, would sooner, would just as soon 后的that从句中,用过去式或过去完成式,表示宁愿做什么I would rather he came tomorrow than today.John would rather that she had not gone to the party yesterday evening.六: 在if only如果....就好了的意思 感叹句中,谓语动词与wish宾语从句的虚拟形式相同.If only he didnt drive so fast!现在If only she had asked someones advice.过去If only the rain would stop.将来 七: 在as if as though 从句中,表示和现在事实相反或对现在情况有所怀疑,用过去式;表示过去想象中的动作或情况, 用过去完成式.He speaks as if he were on the spot.She spoke to me as if I were deaf.This device operated as though it had been repaired.注: 1. 在 as if as though 句中, 如果有可能成为事实, 用陈述语气.He looks as if he is going to be ill.2. 在 insist 后的从句中, 如果是坚持自己, 用陈述语气, 坚持别人做什么事情, 用虚拟语气.She insists that she is right.She insisted that I should finish the work at once.
