3. I didn’t know his telephone number. ____ it, I ____ then.

　　　 A. Had I known, would ring him up　　　　　　 B. Should I know, would have rung him up

　 　　 C. If I knew; would ring him up　　　　　　　　 D. Had I known; would have rung him up

2. If they ____ earlier than expected, they ____ here now.

　　　 A. had started, would be　　　　　　　　　　　　　　　　　 B. started, might be

　　　 C. had started, would have been　　　　　　　　　 D. will start, might have been

1. If I ____ where he lived, I ____ a note to him.

　　　 A. knew, would　　　　　　　　　　　　　　　　　　　　 B. had known, would have sent　　

C. know, would send　　　　　　　　　　　　　　　　 D. knew, would have sent

5、虚拟语气在简单句中的用法

(1)情态动词的过去式用于现在时态时，表示说话人的谦虚、客气、有礼貌，或委婉的语气，常见于日常会话中。如: It would be better for you not to stay up too late. 你最好别太晚睡觉。

(2)在一些习惯表达中。如: I would rather not tell you. 我宁愿不告诉你。

(3)用“may + 动词原形”表示"祝愿"、"但愿”，此时may须置于句首(多用于正式文体中)。如：May you be happy!祝你快乐！May good luck be yours.祝你顺利。 练习、虚拟语气

4、虚拟语气在定语从句中的用法：在"It is time (that) …"句型中，定语从句的谓语动词常用虚拟语气表示将来，动词形式一般用过去式，意思是"该干某事的时候了"。如: It’s (high) time we did our homework. 我们该做作业了。

3、虚拟语气在状语从句中的用法

(1)在带有even if/ even though引导的让步状语从句的主从复合句中，主句和从句都用虚拟语气，动词形式与含有非真实条件句的虚拟语气相同。如: Even if he had been ill, he would have gone t his office. 即使生了病，他俩去办公室。

　 　 (2)由as if或as though引导的状语从句表示比较或方式时。从句谓语形式为动词的过去式(be用were)或 “had十过去分词”。如: He treated me as if I were a stranger. 他那样对待我，好像我是陌

生人似的。She talked about the film as if she had really seen it. 她谈论那部影片，就好像她确实看过一样。

　 注:如果表示的事情可能会发生，那么方式状语从句中的谓语动词可用陈述语气。

(3)在in order that或so that引导的目的状语从句中，谓语动词多用 “could或might(有时也用should)+ 动词原形”。如: Mr green spoke slowly so that his students could (might) hear clearly. 格林先生说得很慢，好让学生听清楚。

l、虚拟语气在主语从句中的用法：在"It is important (strange，natural，necessary)that…"这类句型里，that所引导的主语从句中的谓语动词常用 “should十动词原形”结构，表示某事是"重要"、"奇怪"、"自然"、"必要"等意义。如: It is important that every member (should) inform himself of these rules. 重要的是每个成员知道这些规则。

2、虚拟语气在宾语从句中用法：

(1)在动词wish后的宾语从句中，表示与现在或过去的事实相反，或对将来的主观愿望，从句通常省略连词that。1)表示对现在情况的虚拟:从句动词用过去式或过去进行式(be动词一般用were)。如: I wish I knew the answer to the question. 我希望知道这个问题的答案。(可惜不知道)；2)表示对过去情况的虚拟:从句动词常用"had十过去分词"。如: I wish (wished) I hadn’t spent so much money. 我后悔不该花那么多钱。(实际上已经花掉)；3)表示对将来的主观愿望:谓语动词形式为"would十动词原形"。此时要注意，主句的主语与从句的主语不能相同，因为主句的主语所期望的从句动作能否实现，取决于从句主语的态度或意愿(非动物名词除外)。如: I wish it would stop raining. 但愿雨能停止；I wish you would come soon. 但愿你立刻来。

　　　 (2)在suggest，demand，order，propose，insist，command，request，desire等动词后的宾语从句中，谓语动词用“should + 动词原形”，表示建议、要求、命令等。如: I demand that he (should) answer me immediately. 我要求他立刻答复我。

6、省去条件从句或主句：表示虚拟语气的主句或从句有时可以省略，但其含义仍可以推知。

(1)省去条件从句。如: You could have washed your clothes yourself. 你本可以自已洗衣服的。省去了"If you had wanted to")(事实是:你自己没洗衣服，因为你不想洗。)

(2)省去主句(常用以表示愿望)。如: If my grandmother were with me! 如果我的祖母与我在一起多好啊!(事实是:祖母已不在世。)；If only she had not left! 如果她没走就好了!(事实是:她已经走了。)

5、虚拟条件句可以转换成下列形式:

(l)省略连词if。在书面语中，如果虚拟条件从句中有were，had 或 should，可以把if省略，把这几个词放到主语之前，构成主谓倒装。例如: Should he come (If he should come), tell him to ring me up. 他要是来了，让他给我打个电话。Were I you (If I were you), I would not do it. 我要是你，就不做这事。

　　 (2)用介词短语代替条件状语从句。有时假设的情况并不用条件从句表示出来，而是通过介词短语来表示。如: Without air (If there were not air), there would be no living things. 如果没有空气的话，就不会有生物了。But for your help (If it hadn’t been for your help) I couldn’t have done it. 要是没有你的帮助，我就不可能完成这件事。

　　 假设的情况有时可以通过上下文或其他方式表现出来。如: I was busy that day. Otherwise I would have gone there with them. (If I hadn’t been busy that day, I would have gone there with them.) 我那天很忙，否则，我就和他们一起去那儿了。(如果我那天不忙的话，我就……)；I would have finished the work, but I have been ill. (If I hadn’t been ill, I would have finished the work.) 我本来该完成这项工作的，但我生病了。(如果我没生病的话，我就会完成……)

4、有时条件从句中的动作和主句中的动作发生的时间不一致(表示错综时间的虚拟语气)，这时动词的形式要根据它所表示的时间加以调整。例如: If you had listened to the doctor, you would be all right now. 如果你当初听了医生的话，身体现在就好了。(从句动作指过去，主句动作指现在)