[温故知新]
以前我们学过虚拟语气用于条件状语从句，表示对现在和将来情况的假设。现在我们再来简单复习一下这两种情况并学习对过去情况的假设！
对现在情况的假设：表示现在实际上并不存在的情况。
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条件状语从句 |
主句 |
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与现在事实相反 |
If + 主语 + 动词过去式
（be动词通常用were） |
主语+ would / should / could / might + 动词原形 |
如：If they were here, they would help you.
如果他们在这儿，他们会帮你。
对将来情况的假设：表示将来不大可能实现的情况。
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条件状语从句 |
主句 |
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与将来事实相反 |
A. If+主语+动词过去式
（be动词通常用were）
B． If+主语+were to+动词原形
C． If+主语+should+动词原形 |
主语 + would / should / could / might + 动词原形 |
[小试] 指出下列句子是对哪种情况的假设。
1. If you should succeed, everything would be all right.
2. If you succeeded, everything would be all right.
3. If you were to succeed, everything would be all right.
Key: 1. 对将来情况的假设
2. 对现在或将来情况的假设
3. 对将来情况的假设
请观察下面三个句子，注意主句和从句中谓语动词的使用。
1. In the past, if someone like me had failed to get into university through the college exam, he would have had no chance of getting a degree.
过去，像我这样不能够通过高考而进入大学的人是没有机会拿到学位的。
2. In the past, if someone had worked for a company for over 20 years, they would have stayed there until retirement!
过去，如果一个人在一家公司工作了二十多年，他就会留在那家公司直到退休。
3. If the trees and flowers had been watered more, they would have grown even better.
如果给这些树木和花草多浇一些水的话，它们会长得更好。
这三个句子都表示说话者对过去事实的一种推测，它们都有一种相同的表达方式，即：
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条件状语从句 |
主句 |
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与过去事实相反 |
If + 主语 + 过去完成时 |
主语+ would / should / could / might + have + 过去分词 |
如： If she had worked hard, Susan would have succeeded.
（解析：这句话的意思是：如果苏珊当初努力的话，她早就成功了。事实上她并不努力，所以没有成功。）
If he had not been ill and missed many classes, he would have made progress.
（解析：这句话的意思是：要不是他当时生病缺了许多课，他早就进步了。言下之意是由于他生病缺了许多课，所以他没有取得进步。）
[知识拓展] 虚拟条件句的从句部分如果含有were, should或had, 可将if省略，再把were, should或had 移到从句句首，构成倒装。
If they were here now, they could help us. = Were they here now, they could help us.
If it should rain, the crops would be saved. = Should it rain, the crops would be saved.
If you had come earlier, you would have met him. = Had you come earlier, you would have met him.
[即学即练]
Ⅰ. 翻译下列句子。
1. 如果她有时间，她会跟你一起去的。
2. 如果我是男孩，我就去参军。
3. 如果你能更小心一点，米饭就不会烧焦了。
4. 如果明天下雨，足球赛就要延期。
Ⅱ. 从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
1． ________ fired, your health care and other benefits will not be immediately cut off.（2006 湖北）
A. Would you be B. Should you be
C. Could you be D. Might you be
2． ________ he had not hurt his leg, John would have won the race.(2007全国卷Ⅱ)
A. If B. Since C. Though D. When
Key:
Ⅰ. 1. If she had time, she would go with you.
2. If I were a boy, I would join the army.
3. If you had been more careful, the rice would not have been burnt.
4. If it were to rain tomorrow, the football match would be put off.
Ⅱ. 1. B 2. A