八、虛擬語氣在條件從句(Protasis)中的用法：
條件從句有兩類：（1）真實條件句；（2）虛擬條件句。
如果假設情況有可能發(fā)生的，就是\"真實條件句\"。如：
1. If time permits, we\'ll go fishing together.
(如果有時間的話，我們就一起去釣魚。）
如果假設的情況與事實相反，則為\"虛擬條件句\"。如：
1. If it had rained yesterday, we would have stayed at home.
?。ㄈ绻蛱煜掠甑脑?，我們就會留在家里。）
這回我們要談的就是關于\"虛擬條件句\"的一些句型。
* 這種句子一般由\"從句\"（Subordinate Clause)和\"主句\"(Main Clause)組成。如上
例：
If it had rained yesterday, we would have stayed at home.
\"If it had rained yesterday\" 就是\"從句\"；\"we would have stayed at home\" 則為\"主句。
* 無論\"從句\"或\"主句\"的謂語都要用虛擬語氣。它們所用的動詞有三種時態(tài)
(Tenses)，就是：
現(xiàn)在時態(tài)、過去時態(tài)、將來時態(tài)。
* 句型：
8.1 與現(xiàn)在事實相反的假設(事情的發(fā)生都在同一時間內):
從句：if + 主語 + 動詞的過去式(be 用 were) + ……
主句：主語 + would (should, could , might) + 動詞原形 + ……
1. If I were you, I would go with him.
(從句 If I were you, 主句 I would go with him.)
2. If I were you, I should buy it.
(從句用過去式動詞were，主句用動詞原形 buy)
3. If I had time, I would study French. (如果有時間，我會學習法文。）
（從句用過去式動詞had，主句用動詞原形 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?guī)土恕?
(從句用過去式動詞knew, 主句用動詞原形ask)
注意：如果動作在進行中，主句要用：\"主語 + would be + 進行式動詞 + ……\"
5. If they were here, he would be speaking to them now.
(從句用過去式動詞were, 主句用 would be speaking)
8.2 與過去事實相反的假設(假設從句的事實為過去的事)：
從句：If + 主語 + had +過去完成式動詞 + ……
主句：主語 + would (should, could, might) + have +過去完成式動詞 +……
1. If you had studied harder last term, you could have passed exam.
(從句動詞用had studied, 主句動詞用have passed)
如果你在上個學期用功一些，你就會在考試中過關了。
2. If you had taken my advice, you wouldn\'t have failed in the exam.
(從句動詞用had taken, 主句動詞用have failed)
如果你當時聽從我的勸告的話，你就不會在考試中失敗了。
3. If you had got up earlier, you could have caught the train.
(從句動詞用had got up, 主句動詞用 have caught)
如果你起身得早一點，你就會趕得上火車了。
4. If it had snowed, I would have skied in the park.
(從句動詞用had snowed, 主句動詞用 have skied)
如果下雪的話，我就可在公園里滑雪了。
注意：如果動作在進行中，主句要用：\"I主語 + would + have + 完成進行式動詞+……
5. If they had been here, he would have been speaking to them.
(從句動詞用had been, 主句動詞用 have been speaking)
8.3 與將來的事實可能相反(對將來的事實實現(xiàn)的可能性不大)：
從句：If + 主語 + should (或were) + 動詞原形 +……
主句：主語 + would (could, should, might) + 動詞原形 +……
1. If it should rain, the crops would be saved.
(從句動詞用should rain，主句動詞用 be)
如果天下雨，莊稼可能就收獲了。
2. If he were to go fomorrow, he might tell you.
(從句動詞用were to, 主句動詞用 tell)
如果明天他走的話，他可能會告訴你。
3. If he were here, I would give him the books.
(從句動詞用 were, 主句動詞用 give)
如果他在這兒，我可能會把書給他。
注意：如果動作在進行中，從句(不是主句喔)要用：\"If + 主語 + 過去進行式動詞+……\"
4. If she were staying here now, I would let her ride my horse.
(從句動詞用 were staying, 主句動詞用 let)
如果她現(xiàn)在留在這兒，我可能會讓她騎我的馬。
8.4 從句的 If 有時可省略，那么從句中的動詞(were, had, should)就得移到主語前
面：
1. 原句：If she were younger, she would do it.
去If：Were she younger, she would do it. (把動詞were移到主語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移到主語he的前面)
8.5 有時虛擬條件句的從句或主句都可以省略其中一個：
1. I could help you. (只有主句）
2. If I had time. (只有從句）
3. She should have come to the meeting. (只有主句)
4. If he had much more money. (只有從句)
8.6 有時虛擬條件句的從句和主句地動詞動作時態(tài)會不一致：
8.6.1 從句表示過去，主句表示將來：
If they had started the early morning yesterday, they would be here now.
8.6.2 從句表示將來，主句表示過去：
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 從句表示過去，主句表示將來：
If we hadn\'t made adequate preparations, we shouldn\'t dare to do the
experiment next week.
8.6.4 從句表示將來，主句表示現(xiàn)在：
If we shouldn\'t have an exam this afternoon, I would go shopping now.
