英文文法- If 所引導的假設語氣

If 所引導的假設語氣

 

If 所引導的假設語氣有下列幾種句型:
                                                                                           should
                                                                                           would
1. 表達跟未來事實相反:If+ S+ should+ 原形動詞,S+ could
                                                     were to                          might
                                                    +原形動詞
例:
1. If he should come, I would tell the truth.
2. If the sun were to rise in the west, I would marry you.
3. If photosynthesis(光合作用) were to stop, all living things would disappear.
註:If+ S+ should+原形動詞是表達“一般情況不太可能”,而If+ S+ were to+原形動詞是表達“絕對與事實真理相反”。

 

                                                                       would
                                                                       should
2. 表達跟現在事實相反:If+ S+ were ,S+ could +原形動詞
                                                過去式            might
例:
1. If I were you, I might leave at once.
2. I would buy that house if I had enough money.

 

                                                                           would
                                                                           should
3. 表達與過去事實相反:If+ S+ had+ p.p., S+ could +have+ p.p.
                                                                           Might
例:
1. If you had come to the party, you might have met Jane.
2. He might have come if it had not rained.

 

4. 關於假設語氣應注意事項:
(a) 要利用已知動詞去判斷未知動詞,請思考下列空格的動詞結構
If+ S+ were to+原形動詞,S+____.
S+ might+ have+ p.p.+ if+ ____.
(b) 假設語氣的助動詞一律用過去式,be動詞一律用were。
(c) 假設語氣If子句可以改為倒裝結構,即(1)去掉if,(2)將should, were或had移至主詞前面。
例:
1. If he should come, I would tell the truth.
= Should he come, I would tell the truth.
2. If the sun were to rise in the west, I would marry you.
= Were the sun to rise in the west, I would marry you.
3. If I were you, I might leave at once.
= Were I you, I might leave at once.
4. You might have met Jane if you had come to the party.
= You might have met Jane had you come to the party.
請務必要掌握倒裝結構,才能判斷是與未來、現在、或過去事實相反。

 

                                                                                                 would
                                                                                                 should
(d) 與過去事實相反的事若影響到現在,則主要子句動詞用 could +原形之
                                                                                                 might
結構,這種情況主要子句會有現在的時間副詞出現。
例:
1. If they had built more houses ten years ago, the housing problem would not be so serious now.

 

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If

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