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1、 can, could, may, might都可以都可以用來表示請求或給予許可。但用法用來表示請求或給予許可。但用法上有一些區(qū)別上有一些區(qū)別:1. can與與could can常用于口語中,表示非正式的請求,請求對象一般是家人或朋友。如:a)Can I borrow your bike, Simon? 西蒙,我可以借一下你的自行車嗎? Of course. 當(dāng)然可以。b)Can I have some milk, Mum? 媽媽,我可以喝點(diǎn)牛奶嗎? Yes, you can. 好的。 could是can的過去式,在口語中,could常用來代替can向?qū)Ψ礁竦靥岢稣埱?,用法上比can正式,
2、可以用于向老師或長輩提出請求,這時could不表示過去,回答一般還是用can。如:a) Could I use your computer, please? 請問,我可以用一下你的電腦嗎? Yes, you can. 可以。b) Could I hand in our homework later, Mr Lin? 林老師,我可以稍后交作業(yè)嗎? No, you cant. 不,不行。2. may與與might may也可以用來征求對方意見,意為“可以”,相當(dāng)于could,用法也比can更正式,更禮貌,一般用于向陌生人或所尊敬的人請求許可。如:a) May I ask you a questio
3、n? 我可以問你一個問題嗎? Yes, please. 可以,請問。b) May I come in, Mr Wu? 吳老師,我可以進(jìn)來嗎? No, you may not. 不行。 might是may的過去式,它也可以用來表示征求對方意見,不過很少用。might在語氣上比may更婉轉(zhuǎn),但不如may表現(xiàn)得那么自信,這時might不表示過去時態(tài),肯定回答時通常用may。如:a) Might I join you? 我可以加入你們嗎? Yes, you may. 可以。b) Might I have a look at your new plan? 我可以看一下你的新計劃嗎? No, you ma
4、y not. 不,不行。EXERCISES:1. May I go surfing alone this afternoon, Dad? No, you _. It is dangerous. (2005 江蘇南京) A. may not B. cant C. neednt D. dont 1. 選B。 這里是情態(tài)動詞may 的否定回答。2. Can I get you a drink? _. I have already got one. (2005 甘肅) A. Thats very nice of you. B. No, you dont have to. C. Yes, please.
5、 D. With pleasure. 2. 選B。這里can I 句子是征求意見,所以排除A、D。再根據(jù)下句I have already got one.說明 “不需要”, 故可排除C。3. Lin Lings mother wanted to know _. (2005 四川) A. if she studied hard at school B. how did she study at school C. what did she study at school 3. 選A。 此處為賓語從句,且從句的語序應(yīng)為陳述句語序。 4. Do you want to know _in the fu
6、ture? A special mirror invented by the French scientists can help you. (2006 山東萊蕪) A. what you will look like B. what will you look like C. how do you look like D. how you look like 4. 選 A。 這里是賓語從句,應(yīng)該用陳述句語序,排除B,C;“看上去怎樣”疑問詞應(yīng)該用what, 作為介詞like 的賓語,排除D。5. It is said that the gravity on Mars is only abou
7、t _ of the gravity on Earth. (2006 江蘇蘇州) A. three-eighths B. third-eight C. three-eights D. third-eight 5. 選A。 這里考查的是分?jǐn)?shù)的表達(dá)。 that不能省略的幾種情況不能省略的幾種情況 在由that引導(dǎo)的賓語從句中,由于連詞that只起引導(dǎo)功能,無具體意義,不擔(dān)當(dāng)任何成份,因此在口語或非正式的文體中常可省略。然而,大凡規(guī)則總有例外的情況,在下列that引導(dǎo)的賓語從句中,that則不能省略。1. 從句的主語是從句的主語是that。如:。如: He says that that is a r
8、eal kings hat. 他說那是一個真的王冠。2. that從句中含有主從復(fù)合句。如:從句中含有主從復(fù)合句。如: Im afraid that if youve lost it, you must pay for it.3. 主從句之間有插入語時。如:主從句之間有插入語時。如: It says here, on this card, that it was used in plays. 卡片上寫著,它是古代演戲用的。4. 若出現(xiàn)兩個或兩上以上的由若出現(xiàn)兩個或兩上以上的由that引導(dǎo)的賓語從句,且由并引導(dǎo)的賓語從句,且由并列連詞連接時,只有第一個連詞列連詞連接時,只有第一個連詞that可以
9、省略??梢允÷?。如: She said (that) she would come and that she would also bring her son. 她說她要來,還要帶她的兒子來。IF,WHETHER引導(dǎo)的賓語從句引導(dǎo)的賓語從句. if和和whether引導(dǎo)賓語從句時,作引導(dǎo)賓語從句時,作“是否是否”講,一般情況講,一般情況下,二者沒有區(qū)別,可以換用。但下,二者沒有區(qū)別,可以換用。但if常用于口語中,常用于口語中,whether比較正式。比較正式。如: Millie asked if/whether he liked this sweater. 米莉問他是否喜歡這件羊毛衫。 The
10、 fisherman wants to know if/whether it will rain. 漁民想知道天是否會下雨。 . if和和whether引導(dǎo)賓語從句時,要注意賓語從句三要素,引導(dǎo)賓語從句時,要注意賓語從句三要素,即連詞、語序和時態(tài)。由于即連詞、語序和時態(tài)。由于if和和whether連接的是一般疑連接的是一般疑問句,因此要注意把從句語序改為陳述句語序。問句,因此要注意把從句語序改為陳述句語序。如: Does Mr Zhao live in Room 208? Could you tell me? Could you tell me if/whether Mr Zhao lives
11、 in Room 208? 其次要注意時態(tài)變化: 1. 若主句是一般現(xiàn)在時,從句用任何所需時態(tài)。若主句是一般現(xiàn)在時,從句用任何所需時態(tài)。如: He wants to know if/whether they had a good journey home. 他想知道他們回家旅途是否愉快。2. 若主句是一般過去時,從句則用跟過去相關(guān)的時若主句是一般過去時,從句則用跟過去相關(guān)的時態(tài)。即一般現(xiàn)在時變?yōu)橐话氵^去時、現(xiàn)在進(jìn)行時態(tài)。即一般現(xiàn)在時變?yōu)橐话氵^去時、現(xiàn)在進(jìn)行時變?yōu)檫^去進(jìn)行時、一般將來時為過去將來時、現(xiàn)變?yōu)檫^去進(jìn)行時、一般將來時為過去將來時、現(xiàn)在完成時態(tài)變?yōu)檫^去完成時。在完成時態(tài)變?yōu)檫^去完成時。如
12、: Did the train leave? She didnt know. She didnt know if/whether the train had left. . if和和whether的區(qū)別。的區(qū)別。 二者在下列幾種情況下不能換用:1. 賓語從句置于句首表示強(qiáng)調(diào)時,應(yīng)用賓語從句置于句首表示強(qiáng)調(diào)時,應(yīng)用whether,不用,不用if。如: Whether this is true or not, I cant say. 這是否對,我不能說。2. 賓語從句與賓語從句與or not直接連用時,應(yīng)用直接連用時,應(yīng)用whether, 不能用不能用if。如: I dont know wheth
13、er or not he will come tomorrow. 我不知道他明天是否要來。3. 與動詞不定式連用時,只能用與動詞不定式連用時,只能用whether。如: She cant decide whether to go to America. 她不能決定是否去美國。4. 從句作介詞賓語時,只能用從句作介詞賓語時,只能用whether。如: I worry about whether I hurt her feeling. 我擔(dān)心是否傷了她的感情。5. 賓語從句的謂語動詞是否定形式時,只能用賓語從句的謂語動詞是否定形式時,只能用if,不能用,不能用whether。如: Tom want
14、s know if he wont come here tomorrow. 湯姆想知道他明天是否不來這兒。6. if意為意為“假如,如果假如,如果”時,可以引導(dǎo)條件狀語從句,而時,可以引導(dǎo)條件狀語從句,而whether沒有這個用法。沒有這個用法。如: If Simon comes here tomorrow, Ill call you. 假如西蒙明天來這兒,我將打電話告訴你。選擇填空。選擇填空。1. I dont know if Mr. Wang _on a field trip. If he _ on a field trip tomorrow, please call me. A. goe
15、s; will go B. will go; goes C. will go; will go D. goes; goes 2. She asked me if I knew _. A. whose pen was it B. whose pen it was C. whose pen it is D. whose pen is itExercises:3. They wondered if the teacher _ us English the next term. A. would teach B. had taught C. will teach D. taught4. The boy
16、 asked _ any noise from outside. A. whether had I heard B. whether I had heard C. whether have I heard D. whether I have heard5. I havent decide _ Ill go out or stay at home. A. if B. when C. why D. whether6. I want to know _ he loves you. A. that B. what C. if D. who7. I wondered _ our teacher was
17、going to attend our party. A. whether B. why C. where D. that8. Id like to know _ or not. A. whether will he come B. whether has he come C. whether he will come D. that he will come根據(jù)漢語提示,用英語完成句子。根據(jù)漢語提示,用英語完成句子。1. 我們不知道我們能否在火星上種植植物。 We are wondering _ on Mars.2. 你能告訴我是不是有許多人打算搬到火星上去嗎? Could you tell
18、 me _ to Mars?whether/if we can grow plantsif/whether many people are going to move3. 我不知道他在家洗不洗衣服。 I dont know _ any washing. 4. 我擔(dān)心是否傷害了她的感情。 I was worried about _. whether or not he doeswhether I hurt her feelings1. Uncle Wang came up to see _there was anything wrong with the machine.2. The shop keeper asked my father _ or not he wanted to choose a big Christmas tree. 用用IF/WHETHER填空。填空。if/ whetherwhether3. I dont know _ to go or stay?4. _ that is true, what should we do?whetherIf5. _ they will ever become future Olympic champions, only time will tell. Whether