概念：英语有三种语气，即陈述语气、祈使语气和虚拟语气。陈述语气用于陈述事实、提出看法或问题等，祈使语气用于表示请求、命令或警告等，虚拟语气则表示假想或主观愿望
1.条件句中虚拟语气的形式
时间 | 从句谓语形式 | 主句谓语形式 |
将来 | 动词过去式(be用were) should + 动词原形 were to + 动词原形 |
would / should / might / could + 动词原形 |
现在 | 动词过去式(be 用 were) | would / should / might / could + 动词原形 |
过去 | had +动词过去分词 | would / should / might / could have + 动词过去分词 |
2. 宾语从句中的虚拟语气。
(1) wish
A: 表示与现在和将来事实相反的愿望，从句谓语动词用过去时态。例如：
I wish they were not so late. 要是他们来得不是这么晚就好了。
B: 表示与过去事实相反的愿望，从句谓语动词用过去完成时态。例如：
I wished he hadn't done that. 我真希望那件事不是他做的。
(2) 表示“要求、建议、命令”等动词后面的宾语从句中的虚拟语气。用于此结构的动词有：advise, direct, agree, ask, demand, decide, desire, insist, order, prefer, propose, request, suggest等。从句的谓语动词用“should + 动词原形”，其中should 可以省去。
例如：I insisted that he (should) go with us. 我坚持让他和我们一起去。
注意：当insist 表示“坚持认为”、suggest表示“表明，显示”时，不用虚拟语气。
例如：He insisted that she was honest. 他坚持认为她是诚实的。
3. 主语从句中的虚拟语气。
(1) It be + 形容词 + that... (should)...。用于该句型的形容词有：necessary, good, important, right, wrong, better, natural, proper, funny, strange, surprising等。例如：
It's natural that he should feel hurt. 他感到疼是很正常的。
(2) It be + 过去分词 + that... (should)...。用于该结构中的过去分词是表示“建议、请求、命令”等词的过去分词。如： desired, suggested, requested, ordered, proposed等。例如：
It is desired that the building of the house be completed next month. 真希望这所房子在下个月前就能竣工。
(3) It is time (about time / high time) that... + (过去时或should + 动词原形)...。例如：
It is high time I went home now. = It is high time I should go home. 我该回家了。
(4) 表语从句、同位语从句中的虚拟语气。在suggestion, proposal, order, plan, idea, advice, decision等需要具体内容解释的名词后要使用虚拟语气，其谓语动词为：should + 动词原形，连接从句的that不能省略。例如：
My suggestion is that we should go there at once. 我的建议是我们应该马上去那儿。
4. 省略形式。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。这时，如果出现not等否定词时需放在主语后面。例如：
练习：
1)Had you come five minutes earlier, you______the train to Birmingham. But now you missed it.(《大学英语》(B) Test 1,43)
A. would catch B. would have caught C. could catch D. should catch
解析:B 虚拟语气用法，这里是对过去发生的事情虚拟，用“if从句+had come，主句+would have caught"。此题前面的从句省略 if,所以根据句法要求倒装，将had提前到句首.
2) The dean of the Philosophy Department requested that the visiting scholar________a lecture on the philosopher Sartre.(《大学英语》(B) Test 3,39)
A. gave B. give C. would give D. had given
解析:B request(要求)后面的宾语从句用虚拟语气，从句的谓语动词用“(should)+动词原形
3) 1 wish everybody_______the meeting tomorrow.(《大学英语》(B) Test 4, 36)
A. will attend B. would attend C. had attended D. is going to attend
解析:B wish后的从句用虚拟语气。当表示与将来希望相反时，从句中的谓语动词用" would+动词原形”
4) 1 would rather________two weeks earlier.(《大学英语》(B)Test 4, 45)
A. you should conic here B. you conic here
C. you came here D. you had come here
解析:Do would rather后的从句用过去完成式虚拟过去的情况。
Practice makes perfect. 多多练习，考试才能获得好成绩哦！
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