在英语中学习中，我们常常会碰到各种语气的句子，比如感叹句、祈使句等等。而在GMAT考试中，句子改错的则只有两种语气，那就是陈述语气和虚拟语气。陈述语气主要涉及句子结构及平行的一些考点，而今天小编将带领大家来了解一下GMAT句子改错中的虚拟语气。
　　一、 在GMAT句子改错中，常见的虚拟语气主要是有if引导的，还有名词性从句的虚拟。
　　If条件状语从句的虚拟形式有3种，分别是和过去虚拟、现在虚拟和将来虚拟。要注意的是主从句动词形式的变化。
　　过去：If I had done, I would /could have done...
　　现在：If I were a bird, I would/ could do...
　　将来：If it were to do, I would /could do...
　　和过去虚拟，表示和过去事实相反，比如
　　If I had time, I would attend the meeting.
　　和现在虚拟，表示现在不太可能发生的事。比如
　　If he had hurried, he could have caught the train.
　　和将来虚拟，表示未来发生可能性很小。比如
　　If I were to go abroad ,I would go to America
　　有时条件从句中的动作与主句中的动作，发生的时间不一致，这是动作的形式应根据它所表示的时间加以调整。
　　If you had followed my advice ,you would be better now.
　　If you had studied hard before, you would be a college student now.
　　PS: if条件句有倒装结构，若从句中有had/were/should出现时，把这些词提前，省略if形成倒装结构。
　　例：原句：1: If she were younger, she, would do it.
　　去if：Were she younger, she, would do it.
　　2: If you had come earlier, you would have met him.
　　去if: Had you come earlier, you would have met him.
　　例：Affording strategic proximity to the Strait of Gibraltar, Morocco was also of interest to the French throughout the first half of the twentieth century because they as summed that if they did not hold it, their grip on Algeria was always insecure.
　　(A) if they did not hold it, their grip on Algeria was always insecure
　　(B) without it their grip on Algeria would never be secure
　　(C) their grip on Algeria was not ever secure if they did not hold it
　　(D) without that, they could never be secure about their grip on Algeria
　　(E) never would their grip on Algeria be secure if they did not hold it
　　解析：ACE选项if虚拟语气结构错误，D项that指代不明。
　　二、名词性从句的虚拟也有3种，宾语从句、同位语从句和主语从句的虚拟。
　　1.宾语从句。Advise、suggest、require、request、propose、recommend、command等表示建议命令要求的动词，后面接宾语从句时，从句中的谓语要用动词原形。
　　例：We suggested that theme eting be put off.
　　They insisted that the boy go with them.
　　注意：在GMAT句子改错中，宾语从句的谓语动词不能 should.
　　例：There port recommended that the hospital should eliminate unneeded beds, expensive services should be consolidated, and use sPACe in other hospitals .
　　A、 should eliminate unneeded beds, expensive services should be consolidated, and use space in other hospitals
　　B、 should eliminate unneeded beds, expensive services should be consolidated, and other hospitals' space be used
　　C、 should eliminate unneeded beds, expensive services should be consolidated, and to use space in other hospitals
　　D 、eliminate unneeded beds, consolidate expensive services, and other hospitals' space used
　　E 、eliminate unneeded beds, consolidate expensive services, and use space in other hospitals.
　　解析：ABC选项recommend虚拟语气，should要省略。D eliminate，consolidate和other hospitals' space used 不平行对等。E正确。
　　2. 同位语从句：表示建议、命令、要求等动词的名词形式出现时，同位语从句也要用虚拟语气。从句中谓语用动词原形。
　　例:The budget for education reflects the administration's demand that the money is controlLED by local school districts, but it can only be spent on teachers, not on books, computers, or other materials or activities.
　　A the money is controlled by local school districts, but it can only be spent
　　B the money be controlled by local school districts, but it allows them to spend the money only
　　C the money is to be controlled by local school districts, but allowing it only to be spent
　　D local school districts are in control of the money, but it allows them to spend the money only E local school districts are to be in control of the money, but it can only spend it
　　解析：demand后面的同位语从句要用虚拟语气，is的动词原形是be, 答案B.
　　3. 主语从句：表示个人对事件的反应，比如strange/necessary/important等。主语从句中谓语要用动词原形。
　　例: It is necessary that we make everything ready ahead of time.
　　例：Since chromo some damage may be used by viral infections，medical X-rays，and exposure to sunlight，it is important that the chromo somes of a population to be tested for chemically
　　Induced damage be compared with those of a control population.
　　A to be tested for chemically induced damage be compared with
　　B being tested for damage induced chemically are compared with
　　C being tested for chemically induced damage should be compared to
　　D being tested for chemically induced damage are to be compared to
　　E that is to be tested for chemically induced damage are to be compare able with
　　解析：it is important that.... 主语从句中虚拟，谓语用动词原形be,并且should必须省略。答案A.