謝奎金

由條件狀語從句和主句構(gòu)成的復(fù)合句稱之為條件句，分真實性條件句和非真實性條件句兩種。高考常從以下四個方面對其進(jìn)行考查。

熱點一 根據(jù)前后句邏輯關(guān)系，選擇引導(dǎo)條件狀語從句的從屬連詞

1.引導(dǎo)條件狀語從句常見的從屬連詞有if，unless，in case，on condition that，as（so） long as，if only，only if等。例如：

①—Did you meet with the famous film star？

—If only I had come here earlier.

②I will go with you only if it stays fine tomorrow.

2.引導(dǎo)條件狀語從句較為特殊的從屬連詞的用法。

①provided/providing （that）用于真實情況，表示某事肯定會發(fā)生或一定真實的時候另一事件才會發(fā)生，用法同only if。例如：

Provided the weather is fine，well go on rides.

②supposing/suppose （that）表示“假設(shè)，假定；萬一……怎么辦（同what if...？）”。例如：

Supposing you lost your way，what should you do？

Its not worth the risk，suppose your mother found out.

③but作從屬連詞，用于否定句中，表示“無一例外地”。例如：

Never does a day pass but we need food.

3.從屬連詞unless，in case，if，as long as，once為歷年高考重點，屬高考高頻詞匯，應(yīng)重點把握。注意高考會結(jié)合省略、非謂語動詞在非限定分句“從屬連詞when/unless/once+v-ed/v-ing形式”中加強(qiáng)對連詞的考查。例如：

①Unless youve tried it，you cant imagine how pleasant it is.

②I always take something to read when I go to the doctors in case I have to wait.

③I am sure that Lauras latest play，once staged，will prove a great success.

④Small sailboats can easily turn over in the water if they are not managed carefully.

4.表示條件的從屬連詞as long as，if，unless，once用法區(qū)別。

①as long as用法和only if/on condition that相同，強(qiáng)調(diào)某事的發(fā)生以另一事件的發(fā)生為前提。例如：

As long as I know the money is safe，I shall not worry about it.

②if為正面條件，可能會產(chǎn)生好的或壞的結(jié)果，若某種條件產(chǎn)生壞的結(jié)果，此時的if可用as long as替換。例如：

I would appreciate it if you call back this afternoon for the doctors appointment.

③unless為反面條件，表示“除非，如果不”，故在真實條件句中常和if...not...換用。例如：

I wont call you，unless something unexpected happens.

④once既表時間，又包含條件，譯作“一旦”。例如：

You will be successful in the interview once you have confidence.

熱點二 真實條件句中時態(tài)的選用

1.描述基本事實，在if/in case引導(dǎo)的條件狀語從句中，從句用一般現(xiàn)在時代替將來時，也可使用現(xiàn)在進(jìn)行時或現(xiàn)在完成時，主句使用“將來時或情態(tài)動詞+動詞原形”。例如：

①—What would you do if it rains tomorrow？

—We have to carry it on，since weve got everything ready.

②In such dry weather，the flowers will have to be watered if they are to survive.

2.描述客觀真理、事實或習(xí)慣性動作時，主從句皆用一般現(xiàn)在時，此時if相當(dāng)于whenever；若表示過去習(xí)慣性動作，主從句皆用一般過去時。例如：

Salt is broken down easier if you put it in the hot water.

3.表意愿或委婉語氣，從句使用情態(tài)動詞will/would/should，后接動詞原形，主句時態(tài)不定。例如：

If everyone wont agree，we have to consider the plan again.

If you should have any difficulty finding me，ring me at the number I gave you.

熱點三 非真實條件句中虛擬語氣的用法

1.對現(xiàn)在的假設(shè)。從句用過去時（be動詞一律用were），主句用would/should+do。例如：

If it were not for the fact that she cant sing，I would invite her to the party.

2.對過去的假設(shè)。從句用had done，主句用would/should+have done。例如：

You didnt let me drive.If we had driven in turn，you wouldnt have got so tired.

Look at the trouble I am in!If only I had followed your advice.

3.對將來的假設(shè)。從句用were to+do或should+do，主句用would/should+do。從句使用上述兩種形式時，實現(xiàn)可能性不同。were to +do句型實現(xiàn)可能性最小，也較正式；should+do句型實現(xiàn)可能性最大。例如：

Should you be fired，your health care and other benefits will not be immediately cut off.

4.混合條件句虛擬語氣的用法。若if從句和主句所表示的時間不一致，主從句使用的虛擬語氣形式由主從句所表示的時間確定。做題時重視短語的暗示作用，如as if，but for，if only，even if，otherwise等。例如：

He hesitated for a moment before kicking the ball，otherwise he would have scored a goal.

It is hard for me to imagine what I would be doing today if I had not fallen in love，at the age of seven，with the Melinda Cox Library in my hometown.

熱點四 條件句句式結(jié)構(gòu)的識別及轉(zhuǎn)化

1.條件句兩種常見句型

①if 從句（謂語用一般現(xiàn)在時）+祈使句。例如：

—May I smoke here？

—If you must，choose a seat in the smoking section.

②if 從句（謂語用一般現(xiàn)在時）+主句（謂語用將來時）。例如：

If it rains tomorrow，we just stay at home，watching TV.

2.條件句與祈使句的相互轉(zhuǎn)化

常見祈使句式：動詞原形或名詞詞組+and/or/but+謂語（用將來時或情態(tài)動詞+do）。祈使句與if條件句轉(zhuǎn)化關(guān)系為：

①do...，and you will/wont do=If you do...，you will/wont do...

Lose one hour in the morning and you will be looking for it the rest of the day.

轉(zhuǎn)化為：If you lose one hour in the morning，you will be looking for it the rest of the day.

②do...，or you will do=If you dont do...，you will do...

Start out right away，or youll miss the first train.

轉(zhuǎn)化為：If you dont start out right away，youll miss the first train.

3.條件句的省略

①帶連詞的非限定分句型，即 “連詞+v-ed/v-ing”型省略。注意省略條件，即前后邏輯主語一致，且從句中含有be動詞，將主語和be動詞一并省略，只保留連詞。高考常結(jié)合非謂語動詞對考生進(jìn)行考查，構(gòu)成“連詞+v-ed/v-ing”形式。例如：

—If turned down a second time，will the man have one more try？

—Im sure he will.

②帶連詞的無動詞分句型，即“if+其他”型省略。if 條件句中的省略，如if any/ever/necessary以及if so/not等，其中if ever表頻度，而if much和if any表數(shù)量。例如：

As far as I know，she seldom，if ever，goes down town to visit her friend.

4.only條件句及if條件句的倒裝

①虛擬語氣中不用if時采用倒裝，將助動詞提至句首即可。例如：

What would have happened had Bob walked further，as far as the river bank？

②only置于句首，強(qiáng)調(diào)狀語時，將主句助動詞提至主語之前；注意高考常結(jié)合動詞時態(tài)、語態(tài)對考生進(jìn)行綜合考查。例如：

Only then did she realize how much damage had been caused.

Only after my friend came was the computer repaired.

5.what if...，how about if...，how come的區(qū)別

what if...后接從句，謂語動詞使用一般現(xiàn)在時表將來，譯作“萬一……怎么辦或……怎么樣”，表假設(shè)或征詢對方的意見；how about if同what if，用以詢問對方的意見；how come（that）后接從句，表示對已發(fā)生事件的疑惑，譯作“怎么會”。試比較：

We have so much work to do.What if he doesnt come？

我們有很多工作要做，萬一他不來怎么辦？

We have so much work to do.How come he hasnt come？

我們有很多工作要做，他怎么會到現(xiàn)在還不來呢？

What if/How about if we go to the concert after dinner？

吃過晚飯去欣賞音樂怎么樣