虚拟语气(Subjunctive Mood)这一语法项目几乎是四、六级必考的内容，也是各类英语考试中心测试的重点之一。虚拟语气是一种特殊的动词形式，用来表示说话人所说的话并不是事实，而是一种假设、愿望、怀疑或推测。
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。
1) If places ______ a like, there would be little need for geographers.
A. being B. are C. be D. were
如果各个地方都一样，就不需要地理学家了。(答案是D)
2) If I _____ the meaning of the word, I wouldn't have to look it up.
A. know B. knew C. known D. knowing
如果我知道这个词的意义，就不必查词典了。（答案是B）
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。
例：1995年6月四级第46题
We didn't know his telephone number, otherwise we _____ him,
A) would have telephoned B) must have telephoned
C) would telephone D) had telephoned
本题是与过去时相反的虚拟句，从句中用过去完成式，主句中用would have done。本句相当于if we had known his telephone number，we would have telephoned him。答案是A) would have telephoned。
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 / should /could/ might +动词原形。
例：1996年1月四级第44题
Jean doesn't want to work right away because she thinks that if she ______ a job she probably wouldn't be able to see her friends very often.
A. has to get B. had got C. were to get D. could have got
本句的意思是：“琼不想马上就工作，她认为要是找了工作，就不能经常探访她的朋友了”。 这说明，琼目前没有工作。句中假设的情况在近期内并不会存在。该条件句应当用表示将来情况的虚拟语气。 条件从句的谓语用should或were to引出。 因此C. were to get 是本题答案。选项A. has to get是陈述语气的现在时，不能用于虚拟条件句中。选项B. had got是虚拟语气的过去时，不能表示将来时间。选项D. could have got不能用于虚拟语气的条件从句中。
4. 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。（这种结构在口语中很少使用）。
例：1997年6月四级第42题：
Had he worked harder, he _____ the exams.
A. must have got through B. would have got through
C. would get through D. could get through
本题前半句是表示与过去事实相反的虚拟条件从句，后半句是表示与过去事实相反的主句。相当于：If he had worked harder, he would have got through the exams.本题的答案是B. would have got through。选项A. must have got through（肯定通过）表示一种对过去事情的主观推测，不是与过去事情相反的情况。另外，must不能用在虚拟条件句中。选项C. would get through（就会通过）是虚拟语气现在时的一种表示方法，表示与现在事实相反。选项D. could get through（可能通过），could也可以用于非真实条件句里，表示与事实相反的情况，但这里，它只表示与现在事实或将来可能的事实相反。
5. 有时虚拟条件句并没来if 从句表示出来，而是用介词短语、上下文或其它方式来表示。
例：1995年6月四级第46题
We didn't know his telephone number; otherwise we __________ him.
A. would have telephoned B. would telephone
C. must have telephoned D. had telephoned
结合选项可知, 全句的意思是：“我们不知道他的电话号码，否则我们会打电话给他”。本句中otherwise 引出的是一种与过去事实相反的假设条件， 即实际上没有打电话，因此应选A. would have telephoned。全句相当于：If we had known his telephone number, we would have telephoned him. 选项B. must have telephoned中“must + 完成式”表示“必定……”。选项C. would telephone 的意思是“会打电话”。 因为本题是讲过去发生的情况， 实际上没有打电话，所以不能用would telephone。选项D. had telephoned表示“已经打过电话”，但本题的意思是“没有打过电话”， 所以 D 不是答案。
thank you ,Mr. hong. you are our savior.
