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八、虚拟语气在条件从句(Protasis)中的用法：
条件从句有两类：（1）真实条件句；（2）虚拟条件句。
如果假设情况有可能发生的，就是\"真实条件句\"。如：
1. If time permits, we\'ll go fishing together.
(如果有时间的话，我们就一起去钓鱼。）
如果假设的情况与事实相反，则为\"虚拟条件句\"。如：
1. If it had rained yesterday, we would have stayed at home.
（如果昨天下雨的话，我们就会留在家里。）
这回我们要谈的就是关于\"虚拟条件句\"的一些句型。
* 这种句子一般由\"从句\"（Subordinate Clause)和\"主句\"(Main Clause)组成。如上
例：
If it had rained yesterday, we would have stayed at home.
\"If it had rained yesterday\" 就是\"从句\"；\"we would have stayed at home\" 则为\"主句。
* 无论\"从句\"或\"主句\"的谓语都要用虚拟语气。它们所用的动词有三种时态
(Tenses)，就是：
现在时态、过去时态、将来时态。
* 句型：
8.1 与现在事实相反的假设(事情的发生都在同一时间内):
从句：if + 主语 + 动词的过去式(be 用 were) + ……
主句：主语 + would (should, could , might) + 动词原形 + ……
1. If I were you, I would go with him.
(从句 If I were you, 主句 I would go with him.)
2. If I were you, I should buy it.
(从句用过去式动词were，主句用动词原形 buy)
3. If I had time, I would study French. (如果有时间，我会学习法文。）
（从句用过去式动词had，主句用动词原形 study）
4. If she knew English, she would not ask me for help. (如果她懂英文，她就不必要我帮了。)
(从句用过去式动词knew, 主句用动词原形ask)
注意：如果动作在进行中，主句要用：\"主语 + would be + 进行式动词 + ……\"
5. If they were here, he would be speaking to them now.
(从句用过去式动词were, 主句用 would be speaking)
8.2 与过去事实相反的假设(假设从句的事实为过去的事)：
从句：If + 主语 + had +过去完成式动词 + ……
主句：主语 + would (should, could, might) + have +过去完成式动词 +……
1. If you had studied harder last term, you could have passed exam.
(从句动词用had studied, 主句动词用have passed)
如果你在上个学期用功一些，你就会在考试中过关了。
2. If you had taken my advice, you wouldn\'t have failed in the exam.
(从句动词用had taken, 主句动词用have failed)
如果你当时听从我的劝告的话，你就不会在考试中失败了。
3. If you had got up earlier, you could have caught the train.
(从句动词用had got up, 主句动词用 have caught)
如果你起身得早一点，你就会赶得上火车了。
4. If it had snowed, I would have skied in the park.
(从句动词用had snowed, 主句动词用 have skied)
如果下雪的话，我就可在公园里滑雪了。
注意：如果动作在进行中，主句要用：\"I主语 + would + have + 完成进行式动词+……
5. If they had been here, he would have been speaking to them.
(从句动词用had been, 主句动词用 have been speaking)
8.3 与将来的事实可能相反(对将来的事实实现的可能性不大)：
从句：If + 主语 + should (或were) + 动词原形 +……
主句：主语 + would (could, should, might) + 动词原形 +……
1. If it should rain, the crops would be saved.
(从句动词用should rain，主句动词用 be)
如果天下雨，庄稼可能就收获了。
2. If he were to go fomorrow, he might tell you.
(从句动词用were to, 主句动词用 tell)
如果明天他走的话，他可能会告诉你。
3. If he were here, I would give him the books.
(从句动词用 were, 主句动词用 give)
如果他在这儿，我可能会把书给他。
注意：如果动作在进行中，从句(不是主句喔)要用：\"If + 主语 + 过去进行式动词+……\"
4. If she were staying here now, I would let her ride my horse.
(从句动词用 were staying, 主句动词用 let)
如果她现在留在这儿，我可能会让她骑我的马。
8.4 从句的 If 有时可省略，那么从句中的动词(were, had, should)就得移到主语前
面：
1. 原句：If she were younger, she would do it.
去If：Were she younger, she would do it. (把动词were移到主语she的前面)
2. 原句：If he had tried it, he could have done it.
去If：Had he tried it, he could have done it.(把had移到主语he的前面)
8.5 有时虚拟条件句的从句或主句都可以省略其中一个：
1. I could help you. (只有主句）
2. If I had time. (只有从句）
3. She should have come to the meeting. (只有主句)
4. If he had much more money. (只有从句)
8.6 有时虚拟条件句的从句和主句地动词动作时态会不一致：
8.6.1 从句表示过去，主句表示将来：
If they had started the early morning yesterday, they would be here now.
8.6.2 从句表示将来，主句表示过去：
If I were not to make a preparation for my experiment this afternoon, I
would have gone to see the film with you last night.
8.6.3 从句表示过去，主句表示将来：
If we hadn\'t made adequate preparations, we shouldn\'t dare to do the
experiment next week.
8.6.4 从句表示将来，主句表示现在：
If we shouldn\'t have an exam this afternoon, I would go shopping now.
