最佳答案since+时间点for+时间段eg:He has kept the book for two weeks.He borrowed the book since two weeks ago.注意动词的时态，for后面是一段时间，动词用完成式，而since后面是一个时间点，动词用过去式。

两周前的一天，与for two weeks 的两个星期这样14天相比是一个点。

一、延续性动词延续性动词表示的动作不但可以延续，而且可以产生持久的影响。

常见的这类动词有：be，have，keep，know，learn，lie，live，read，sing，sleep，stand，stay，wait，walk，watch等。

延续性动词的用法很广，但常见于现在完成时中的句子中，且常与for，how，long，since等引导的表示一段时间的状语或状语从句连用。

例如：1．I have learned more than 1，000 Chinese words since I came to China．自从来到中国，我已经学会了l，000多个汉字。

2．We have lived in Linqing since we came here．自从来到这儿，我们就一直住在临清。

3．I have kept the picture for about three years．这张画我保存了大约三年。

二、终止性动词终止性动词又称为瞬间动词或非延续性动词，它表示的动作不能延续，也就是说动作一旦发生就立即结束，并产生某种结果。

常见的这类动词有：accept，arrive，become，begin，borrow，break，buy，catch，close，come，die，end，fall，finish，get，give，go，join，leave，put，reach，receive，shut，start，stop等。

终止性动词用在现在完成时要注意下面三点：（一）终止性动词可直接用来表示某一动作的完成。

例如：1．They have reached Shanghai．他们已经到达了上海。

2．Has he gone to London? 他已经到伦敦去了吗?（二）终止性动词表示的动作极其短暂，不能持续，所以，在现在完成时中一般不能和以since，for等引导的表示一段时间的状语连用。

例如：1．那老人已经死了一周了。

The old man has died for a week．(误) 2．他三天前就已经来这儿了。

He has come here since three days ago．(误)在以上两句中，die和come都是终止性动词，可用于现在完成时，但不能与以since或for引导的表示一段时间的状语连用。

那么，上面两个句子应该怎样译成英语呢?请看下面四种译法：1．把终止性动词改为延续性的动词。

例如：①The old man has been dead for a week．②He has been here since three days ago．2．把原句中的一段时间改为表示“过去”的时间，时态由现在完成时改变成一般过去时。

例如：①The old man died a week ago．②He came here three days ago．3．用“It is+时间+since…”句式。

例如：①It is／has been a week since the old man died．②It has been／is three days since he came here．4．用“多长时间+has passed+since…”句式。

例如：①A week has passed since the old men died．②Three days had passed since he came here．(三)有关特殊终止性动词的用法。

1．在while(表示一段时间)引导的从句里，谓语动词不能使用终止性动词，但可以把while改成when，这样，从句里的谓语动词就可以使用终止性动词了。

因为when既可以表示时间的“点”，又可以表示时间的“段”。

例如：While he got to America．he found his English Was very poor．(误)When he got t0 America．he found his English was very poor．(正)2．终止性动词的否定式与until连用时，意为“直到……才／不到什么时间不……”等。

例如：Don’t get off until the bus stops．车未停稳，切勿下车。

3．终止性动词不可以与how long引导的句式连用。

例如：How long have you borrowed the magazine?(误)When did you borrow the magazine?(正)How long have you kept the magazine?(正)教学参考：从中考试题透视瞬间动词和延续性动词2004/04/28 13:00 英语辅导报请看两道中考试题：1.-How long have you ________ the book?-Two weeks.A. boughtB. lentC. hadD. borrowed(2002四川眉山)[Key:C]2. -Do you know him well?-Sure, we________friends for ten years.A. wereB. have beenC. have becomeD. have made(2002河北)[Key:B]从考生答卷上看，许多考生都误选了1. A、D 2. C、D。

究其原因，是学生对瞬间动词与延续性动词的用法未掌握的缘故。

笔者现将这两类动词的含义、用法等作以归纳。

一、瞬间动词和延续性动词的含义及用法1.瞬间动词是指动作短暂、不长久的动词，如begin, become, sell, buy, borrow等。

其用法有：①有一般时态、进行时态和完成时态。

例如：They began classes at eight this morning.今天上午他们八点钟开始上课的。

(一般过去时)I'm coming, Mum.妈妈，我就来。

(现在进行时)The train hasn't arrived yet.火车还未到达。

(现在完成时) ②常与点时间连用。

例如：She often goes to bed at ten.她经常十点钟睡觉。

③不能与段时间连用。

例如：He has joined the army for two years. (×)She has come here for half an hour. (×)2.延续性动词是指长久的、可以延续的动词，如sleep, know, keep, wait, study等。

其用法为：①有各种时态。

例如：They knew each other last year.他们去年就彼此相识。

(过去时)We'll learn Russian next year.明年我们要学俄语。

(将来时) ②常与段时间连用。

例如：Mr Zhang has lived here for two years.张先生在这儿住了两年了。

He has taught there since 1987.自1987年来他一直在那儿教书。

③不与点时间连用(do, have, eat等除外)。

例如：Mary has worked at eight. (×)She walked at five yesterday. (×)二、避免瞬间动词和延续性动词与时间误用的方法1.避免瞬间动词与段时间误用，可以用以下五种方法：①用ago这个词。

例如：他买了这本书两年了。

误：He has bought the book for two years.正：He bought the book two years ago.②将瞬间动词用相同或相近的延续性动词(短语)代替。

例如：他们认识5年了。

误：They have got to know each other for five years.正：They have known each other for five years.③将瞬间动词用意义相同的形容词或分词(副词)短语作表语的形式来代替。

例如：他父亲死了五年了。

误：His father has died for two years.正：His father has beendead for two years.④运用句型It is (has been)…since…来表达。

例如：汤姆参军4年了。

误：Tom has joined thearmy for four years.正：It is (has been) four years since Tom joined the army.⑤用瞬间动词的否定结构来表达。

例如：直到父母回来他才睡觉。

误：He went to bed until his parents came home.正：He didn't go to bed until his parents came home.2.避免延续性动词与点时间状语误用的方法有：①用延续性动词的进行时态来表达。

例如：昨晚十点钟他正学英语。

误：He studied English at ten o'clock last night.正：He was studying English at ten o'clock last night.②在延续性动词前加begin等瞬间性动词来表达。

例如：玛丽8点钟工作。

误：Mary worked at eight o'clock.正：Mary began to work at eight o'clock.三、瞬间动词与延续性动词在时间状语从句中的运用1.在以when, as soon as, as, before, after等引导的时间状语从句中，谓语动词既可以是瞬间性的，也可以是延续性的。

例如：When he came in, I was doing some washing.他进来时，我正在洗衣服。

We often take a nap after we have meal.饭后，我们常常要小睡一下。

2.在以while引导的时间状语从句中，谓语动词只能是延续性的。

例如：While they were working, they saw something strange in the sky.当他们在劳动时，他们看见天空中有些奇怪的东西。