| before和ago都能表示在一段時(shí)間以前，但是二者的內(nèi)涵和具體用法有明顯的區(qū)別： 1. before表示從過去或?qū)砟骋粫r(shí)間算起多少時(shí)間以前，由于與這一時(shí)間狀語連用的行為先發(fā)生在過去或?qū)砟骋粫r(shí)刻之前，因此往往出現(xiàn)在過去完成時(shí)態(tài)或?qū)硗瓿蓵r(shí)態(tài)中。例如： ① I called him up last night， but his mother told me he had left for Wuhan two days before. ② She said that she had married him five years before. 2.如果不具體表明多少時(shí)間以前，before意為'從前；以前'，表示從現(xiàn)在開始追溯到過去一段時(shí)間，或者主句的謂語動詞表示的是經(jīng)常、反復(fù)發(fā)生的行為，以副詞的形式置于句末，可以用在現(xiàn)在完成時(shí)態(tài)中。例如： ①I have never been to Beijing before. ②Have you ever seen a tiger before? ③ I often go over the lessons that I have learned a few days before. 注意： before前的時(shí)間狀語如果是特定的，含義不一樣。試比較： He said he had arrived here a day before. (一天前) He said he had arrived here the day before. (前一天) 3. ago指的是從現(xiàn)在起到過去時(shí)間的某一點(diǎn)的一段時(shí)間。這個時(shí)間狀語常與一般過去時(shí)態(tài)或過去進(jìn)行時(shí)態(tài)連用。例如： ① I graduated from the college twenty years ago. ②I was asked what I was doing a month ago. 4. 表示在某一時(shí)間點(diǎn)或事件以前時(shí)，只能用before，不用ago。因?yàn)檫@種用法是將before當(dāng)作介詞或連詞使用。ago不具有這種功能。例如： ① He will come back before eleven o'clock. ② Where did your brother study before he joined the army? ③ It was hoped that this would be achieved before the year 2006. 5.按語法規(guī)則，ago只能與一般過去時(shí)連用，但在since three years ago這類短語中能與現(xiàn)在完成時(shí)態(tài)連用。因?yàn)閠hree years ago構(gòu)成一個名詞短語，共同作since的賓格，意為'自從三年前以來'。例如： ① He has been here since three years ago. ② I have taught English in this school since twenty years ago. 6. 含before的從句一般不用將來時(shí)態(tài)，如果采用'will / would +V.'時(shí)，一般被認(rèn)為是情態(tài)或虛擬語氣。例如： I would die before I would confess to it. 7.如果before從句是一般過去時(shí)態(tài)，所暗示的是過去發(fā)生的事，主句則宜用過去完成時(shí)，語義偏重于過去某階段的行為或狀況時(shí)，還可與一般過去時(shí)態(tài)連用。例如： ① I had never seen a Red Army man before I arrived in Xi'an. ② They asked me things that happened before the boy was born. 8. 不少的語法書上說，before引導(dǎo)的從句習(xí)慣上不與否定的主句連用，要用until。實(shí)際上二者都可以，有時(shí)在意義上有些區(qū)別。試比較： He didn't arrive until I returned. 直到我回來時(shí)他才到達(dá)。 He did not arrive before I returned. 在我回來之前他尚未到達(dá)。 I didn't manage to do it until you had explained how. 直到你解釋了如何干，我才設(shè)法完成了那項(xiàng)工作。 I didn't manage to do it before you had explained how. 你解釋了如何干之后，我才設(shè)法完成了那件工作。 9. before在句中的含義比較靈活，雖然before引導(dǎo)的也是一個時(shí)間狀語，但譯成漢語時(shí)卻不必死譯為'在……以前'?？梢圆扇∠旅鎺追N譯法：(A)譯為'……才'；(B)譯為'……就'；(C)譯為'尚未'、'還沒有'、'來不及'、'不要'、'別'；(D)譯為'在……的時(shí)候還沒有'；(E)譯為'如果'、'否則'、'免得'；(F)譯為'到'、'等到'、'沒等……就'；(G)譯為'然后'等。例如： A. It will be five years before we meet again. 要等五年我們才能再見面。 We waited a long time before the train arrived. 我們等了很長時(shí)間火車才到達(dá)。 B. I hadn't waited long before he came. 我沒等多久他就來了。 He had not gone a mile before he felt tired. 還沒走一英里路，他就覺得累了。 C. His father died before he was born. 他尚未出世他父親就去世了。 Catch him before he escapes. 抓住他，別讓他跑了。 Take this computer before you change your mind. 買了這臺電腦，不要三心二意了。 D. We arrived there before it began to rain. 我們到達(dá)那里的時(shí)候還沒下雨。 E. Go before I call the police. 走吧，否則我叫警察了。 I had better go now before it is too late. 我最好現(xiàn)在就走，免得太遲。 Pigs will fly before he'll be a scientist. 如果他當(dāng)科學(xué)家，豬都會飛了。 F. The crops will die before the rain fall. 等到天下雨，莊稼早枯死了。 Before I could sit down, he offered me a cup of tea. 沒等我坐下，他就給我端上一杯茶。 G. I shaved before I went to the party. 我刮了臉，然后去參加宴會。 |
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