2018年9月大学英语B考试马上开始，小编为各位参加大学英语B考试的考生整理了一些练习，各位考生赶紧练起来吧！
大学英语B级语法结构精讲——虚拟语气
语气是动词的一种形式，它表示说话人对某一行为或事情的看法和态度。虚拟语气表示动作或状态不是客观存在的事实，而是说话人的主观愿望、假设或推测等。
虚拟语气在条件从句中的用法
条件句有两类，一类是真实条件句;一类是非真实条件句，也就是虚拟条件句。
如果假设的情况是有可能发生的，就是真实条件句，谓语要用陈述语气。
如I fit doesn’t rain tomorrow, we will go to the park.
如果假设的情况是过去或现在都不存在的，或将来不大可能发生的，则是虚拟条件句。
如If he had seen you yesterday, he would have asked you about it.
在含有虚拟条件句的复合句中，它的基本特点是时态退后。
列表如下：
(1)同现在事实相反的假设
句型：
条件从句 | 主句 |
一般过去时 | should( would) +动词原形 |
例：If they were here, they would help you.(要是他们在这儿，他们就能帮你了。)
(2)表示与过去事实相反的假设
句型：
条件从句 | 主句 |
过去完成时 | should(would) have+ 过去分词 |
例：The rice would not have been burnt if you had been more careful.
(3)表示对将来的假想
句型：
条件从句 | 主句 |
一般过去时 | should( would) +动词原形 |
were+ 不定式 | |
should+ 动词原形 |
例：If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were to succeed, everything would be all right.
注意：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，实行倒装。例如：
Were they here now, they could help us.(要是他们在这儿，他们就能帮我们了。)=If they were here now, they could help us.
Had you come earlier, you would have met him.(你要是早点来，就可能碰见他了。)=If you had come earlier, you would have met him.
Should it rain, the crops would be saved.(要是下雨，庄稼或许能得救。)=If it should rain, the crops would be saved.
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