2019-2020年八年級(jí)英語(yǔ) 語(yǔ)法賓語(yǔ)條件從句教案A if從句中的動(dòng)詞是一般現(xiàn)在時(shí)，主句的動(dòng)詞是一般將來(lái)時(shí)。主句和從句的先后次序無(wú)關(guān)緊要。If he runs hell get there in time如果他跑步去就會(huì)及時(shí)趕到那里。The cat will scratch you if you pull her tail如果你拉貓的尾巴，它會(huì)抓你。這種類(lèi)型的句子意味著if從句中的動(dòng)作很可能發(fā)生。注意：這里的含義是現(xiàn)在或?qū)?lái)，但if從句中的動(dòng)詞是一般現(xiàn)在時(shí)而不是一般將來(lái)時(shí)。if+willwould只能用于表示某些特殊含義時(shí)。（參見(jiàn)第224節(jié)。）B 基本形式可能的變化形式1 主句的變化除if+一般現(xiàn)在時(shí)+一般將來(lái)時(shí)外，可能是：（a）if+一般現(xiàn)在時(shí)+maymight（可能性）If the fog gets thicker the plane maymight be diverted如果霧再大，飛機(jī)就可能改飛別的機(jī)場(chǎng)降落。（也許飛機(jī)確實(shí)會(huì)改飛別的機(jī)場(chǎng)降落。）（b） if+一般現(xiàn)在時(shí)+ may（允許）can（允許或能力）If your documents are in order you maycan leave at once如果你的證明文件都齊備了你可以馬上就走。（允許）If it stops snowing we can go out如果雪停了我們就可以出去了。（允許或能力）（c）if+一般現(xiàn)在時(shí)+must，should或任何表示命令、請(qǐng)求或勸告的形式：If you want to lose weight you mustshould eat less bread如果你想減輕體重，你必須應(yīng)該少吃面包。If you want to lose weight you had better eat less bread如果你想減輕體重，最好少吃面包。If you want to lose weight eat less bread如果你想減輕體重，少吃面包。If you see Tom tomorrow could you ask him to ring me？如果你明天見(jiàn)到湯姆，你能讓他給我打個(gè)電話(huà)嗎？（d）if+一般現(xiàn)在時(shí)+一般現(xiàn)在時(shí)if+兩個(gè)一般現(xiàn)在時(shí)可以用來(lái)表示自動(dòng)產(chǎn)生或照例會(huì)產(chǎn)生的結(jié)果：If you heat ice it turns to water如果把冰加熱，它就化成水。（也可以用will turn。）If there is a shortage of any product prices of that product go up如果某種產(chǎn)品短缺，那種產(chǎn)品的價(jià)格就上漲。（e）當(dāng)if用來(lái)表示 assince（參見(jiàn)第338節(jié)A）時(shí)，主句中就可能使用多種不同時(shí)態(tài)：Ann hates LondonIf she hates it why does she live there？she ought to move out安討厭倫敦。既然她討厭倫敦，她為什么還住在那里？她應(yīng)當(dāng)搬走。（If she hates it可用If so來(lái)代替。）當(dāng)然這已不是一個(gè)真正的條件句了。2 if從句的各種變化形式if+一般現(xiàn)在時(shí)可能用下列時(shí)態(tài)替代以表示條件：（a）if+現(xiàn)在進(jìn)行時(shí)，表示現(xiàn)在的動(dòng)作或?qū)?lái)的安排：If you are waiting for a bus youd better join the queue如果你是在等公共汽車(chē)，你最好排隊(duì)。（現(xiàn)在的動(dòng)作）If you are looking for Peter youll find him upstairs如果你是在找彼得，到樓上就會(huì)找到他。（現(xiàn)在的動(dòng)作）If you are staying for another night Ill ask the manager to give you a better room如果你還要住一夜，我就請(qǐng)經(jīng)理給你安排一個(gè)好一點(diǎn)的房間。（將來(lái)的安排）（b）if+現(xiàn)在完成時(shí)：If you have finished dinner Ill ask the waiter for the bill如果你吃完了，我就叫侍者來(lái)算帳。If he has written the letter Ill post it如果他寫(xiě)完了信，我就把它寄走。If they havent seen the museum wed better go there today如果他們沒(méi)參觀過(guò)那個(gè)博物館，我們今天最好去那里。222 條件句類(lèi)型2 A if從句中的動(dòng)詞用一般過(guò)去時(shí)，主句中的動(dòng)詞用條件時(shí)態(tài)：If I had a map I would lend it to you我要有地圖就借給你。（但我沒(méi)有地圖。句子的含義是指現(xiàn)在。）If someone tried to blackmail me I would tell the police如果有人企圖敲詐我，我就向警察告發(fā)。（但我想不會(huì)有人敲詐我。句子的含義是指將來(lái)。）第一類(lèi)和第二類(lèi)條件句之間并不存在時(shí)間上的差別。像第一類(lèi)條件句一樣，第二類(lèi)指的是現(xiàn)在或?qū)?lái)； if從句中的過(guò)去時(shí)不是真正的過(guò)去時(shí)，只是一種虛擬語(yǔ)氣，表示不真實(shí)（如上述第一個(gè)例子）或不大可能（如上述第二個(gè)例子）。B 類(lèi)型2有以下用法：1 所假設(shè)的事與已知的事實(shí)相反時(shí)：If I lived near my office Id be in time for work要是我住的離辦公樓近，我上班就不會(huì)遲到。（但我不住在辦公樓附近。）If I were you Id plant some trees round the house如果我是你的話(huà)，我就會(huì)在房子周?chē)N一些樹(shù)。（但我不是你。）2 說(shuō)話(huà)人認(rèn)為從句中的動(dòng)作不會(huì)發(fā)生時(shí)：If a burglar came into my room at night Id scream要是半夜三更竊賊闖進(jìn)我的房間，我就會(huì)拼命叫喊。（但我不認(rèn)為會(huì)有竊賊闖入我的房間。）If I dyed my hair blue everyone would laugh at me要是我把頭發(fā)染成藍(lán)色，大家就要笑我了。（但我不想染它。）有些if從句可以有上述兩種含義中的一種：If he left his bicycle outside someone would steal it要是他把自行車(chē)放在外面，會(huì)有人把它偷走。If he left his bicycle可以意指可他沒(méi)有（如上述 1中的用法，指的是現(xiàn)在）或他沒(méi)這么打算（如上述2中的用法，指的是將來(lái)）。但真正的含義通常從上下文中可以看清楚。這種語(yǔ)義混淆可以通過(guò)使用werewas+不定式而不用上述類(lèi)型2中的一般過(guò)去時(shí)來(lái)避免。if hesheit were可以代替 if hesheit was，而且被認(rèn)為是更正確的形式：If he were to resign相當(dāng)于：If he resigned他萬(wàn)一（果真）要辭職的話(huà)If I were to succeed相當(dāng)于：If I succeeded我竟然（果真）會(huì)成功的話(huà)were的這種用法主要見(jiàn)于相當(dāng)正式的句子里。if hesheit was+不定式在日?？谡Z(yǔ)中是可以的，但是如上例所示那樣使用過(guò)去時(shí)態(tài)更為常見(jiàn)。3 有時(shí)類(lèi)型2可以用做類(lèi)型1的替代形式，表示完全有可能實(shí)現(xiàn)的計(jì)劃和建議。這種用法頗易引起混淆：Will Mary be in time if she gets the ten oclock bus？No，but shed be in time if she go the ninethirty busNo， but shell be in time if she gets the ninethirty bus如果瑪麗趕上10點(diǎn)鐘的公共汽車(chē)，她會(huì)及時(shí)到達(dá)嗎？不會(huì)的，但是如果她趕上9點(diǎn)30分的汽車(chē)，她就會(huì)及時(shí)到達(dá)。Well never save 100！If we each saved 10 a week wed do it in ten weeksIf we each save 10 a week well do it in ten weeks我們永遠(yuǎn)攢不了100英鎊！要是我們每人每周儲(chǔ)蓄十英鎊，我們?cè)谑芎缶蜁?huì)做到。以類(lèi)型2的形式表示建議要比以類(lèi)型1的形式有禮貌些，就如同用would you表示要求要比will you更有禮貌一樣。但學(xué)生不必在類(lèi)型2的這種用法上花過(guò)多工夫。C 基本形式可能的變化形式1 主句的變化（a）可以用might或could而不用 would：If you tried again you would succeed要是你再試一試，你會(huì)成功的。（可靠的結(jié)果）If you tried again you might succeed要是你再試一試，可能會(huì)成功。（可能的結(jié)果）If I knew her number I could ring her up要是我知道她的號(hào)碼，就能給她打電話(huà)。（能力）If he had a permit he could get a job要是他有許可證的話(huà)，就可以找到工作。（能力或允許）（b）可以用條件時(shí)態(tài)中的進(jìn)行時(shí)而不用其一般時(shí)：Peter is on holiday；he is touring ItalyIf I were on holiday I wouldmight be touring Italy too彼得在休假，他在意大利旅游。如果我在休假，我也會(huì)（可能）在意大利旅游。（c）希望表達(dá)過(guò)去自動(dòng)的或習(xí)慣性的反應(yīng)時(shí)，可以在if+過(guò)去時(shí)后再跟一個(gè)過(guò)去時(shí)?？梢耘c第221節(jié)B1（d）所提到if+兩個(gè)現(xiàn)在時(shí)態(tài)相比較。注意：這里的過(guò)去時(shí)具有過(guò)去的含義：If anyone interrupted him he got angry如果有人打擾他，他就會(huì)生氣。（每當(dāng)有人打擾他時(shí)）If there was a scarcity of anything，prices of that thing went up如果什么物品短缺，那種物品的價(jià)格就會(huì)上漲。（d）當(dāng)if用來(lái)表示as或since的時(shí)候，主句中可能用各種時(shí)態(tài)。這里if+過(guò)去時(shí)態(tài)具有過(guò)去的含義。這種句子并不是真正的條件句。The pills made him dizzyAll the same he boughthas boughtis buying some moreIf they made him dizzy why did he buyhas he boughtis he buying more？那種藥使他頭暈。盡管如此，他還是又買(mǎi)了一些又再買(mǎi)了一些還要再買(mǎi)一些。如果那些藥使他頭暈，那他為什么還買(mǎi)了買(mǎi)還準(zhǔn)備再買(mǎi)？I knew she was short of moneyIf you knew she was short of money you should have lent her somewhy didnt you lend her some？我知道她缺錢(qián)。如果你知道她缺錢(qián)，你應(yīng)該借給她一些。你為什么不借給她一些？2 if從句的各種變化有時(shí)不用if+一般過(guò)去時(shí)，而可以用下列各種時(shí)態(tài)：（a）if+過(guò)去進(jìn)行時(shí)（Were going by air and）I hate flyingIf we were going by boat Id feel much happier（我們準(zhǔn)備乘飛機(jī)去而）我討厭乘飛機(jī)。要是我們乘船去的話(huà)我會(huì)感到愉快得多。If my car was working I wouldcould drive you to the station要不是我的車(chē)壞了，我會(huì)開(kāi)車(chē)送你去車(chē)站的。（b）if+過(guò)去完成時(shí)If he had taken my advice he would have heen a rich man now如果他聽(tīng)了我的勸告，他現(xiàn)在會(huì)是一個(gè)有錢(qián)人了。（這是類(lèi)型2和類(lèi)型3的混合用法。第223節(jié)中將再舉一些這種例子。）（關(guān)于ifwould，參見(jiàn)第224節(jié)。）223 條件句類(lèi)型3A if從句中的動(dòng)詞用過(guò)去完成時(shí)，主句中的動(dòng)詞用條件完成時(shí)。這種句子所指的時(shí)間是過(guò)去；所提出的條件是不可能實(shí)現(xiàn)的，因?yàn)閕f從句中的動(dòng)作在過(guò)去并未發(fā)生。If I had known that you were ing I would have met you at the airport要是我早知道你要來(lái)的話(huà)，我就會(huì)在機(jī)場(chǎng)接你了。（但我不知道，所以我也沒(méi)去。）If he had tried to leave the country he would have been stopped at the frontier要是他當(dāng)時(shí)試圖離開(kāi)這個(gè)國(guó)家，他就會(huì)在邊界被阻攔。（但他并未這樣做。）B 基本形式可能的變化形式1 可以用could或might而不用would：If we had found him earlier we could have saved his life要是我們那時(shí)早點(diǎn)找到他的話(huà)，我們會(huì)把他救活的。（能力）If we had found him earlier we might have saved his life要是我們那時(shí)早點(diǎn)找到他的話(huà)，我們可能會(huì)把他救活的。（可能性）If our documents had been in order we could have left at once要是我們的證明文件都齊備的話(huà)，我們那時(shí)就能夠馬上走。（能力或允許）2 可以用條件完成進(jìn)行時(shí)：At the time of the accident I was sitting in the back of the car，because Toms little boy was sitting beside him in frontIf Toms boy had not been there I would have been sitting in front事故發(fā)生的時(shí)候，我坐在車(chē)子的后座，因?yàn)闇返男鹤幼谇斑吽纳砼?。要是湯姆的孩子沒(méi)坐在那里的話(huà)，我就會(huì)坐在前面了。3 可以在if從句中用過(guò)去完成進(jìn)行時(shí)：I was wearing a seat beltIf I hadnt been wearing one Id have been seriously injured我當(dāng)時(shí)系了安全帶。要是沒(méi)有系上的話(huà)，我就會(huì)受重傷了。4 可以把類(lèi)型2和類(lèi)型3結(jié)合起來(lái)：The plane I intended to catch crashed and everyone was killedIf I had caught that plane I would be dead nowI would have been killed我原想趕乘的那架飛機(jī)墜毀了，所有乘客都遇難身亡。要是我趕上了那架飛機(jī)，我也就沒(méi)命了我就會(huì)摔死了。（類(lèi)型 3）If I had worked harder at school I would be sitting in a fortable office now；I wouldnt be sweeping the streets要是在上學(xué)時(shí)學(xué)習(xí)再努力一些，我現(xiàn)在就會(huì)坐在舒適的辦公室里，而不會(huì)是在掃大街了。（但我上學(xué)時(shí)不努力，因而我現(xiàn)在在掃大街。）5 had可以位于句首并省略if：If you had obeyed orders this disaster would not have happened相當(dāng)于：Had you obeyed orders this disaster would not have happened要是你當(dāng)時(shí)服從了命令，這場(chǎng)災(zāi)難就不會(huì)發(fā)生了。