if、 whether 用法总结
whether,if
if和whether通用，都表示“是否”的意思。一般来说，后者比较正式，在口语中前者常用来代替后者。但两者有时具有不同的暗示。用whether时，正反两面的选择意义较强，问话人并不在意回答是肯定还是否定；而用if时，则比较强调单方面，即正面，问话人希望得到肯定的回答。另外，还要注意以下几点：
一、whether和if都可以与or not连用；但写在一起时，只能用whether，不能用if。如：
I don't care whether (或if) it will rain or not．
I don't care whether or not it will rain. (不用if)
二、在引导宾语从句时，应注意：
1、表示“是否”时，两词都能引导宾语从句。
I wonder if/whether you can examine him now．
2、宾语从句移置句首时，用whether，不用if。
Whether it is true or not，I can't say．
3、宾语从句为否定形式时，通常用if，而不用whether。
I asked Tom if Mary wouldn’t come．
4、作discuss等词的宾语，用whether不用if。
We discussed whether we should buy the gift for him．
三、在下列情况下，只能用whether，不能用if。
1、与不定式连用时，只能用whether．
He can't decide whether to accept or refuse．
2、在介词后，只能用whether。
Everything depends on whether he is ready．
3、在名词后作同位语时，只能用whether。
The question whether they ought to stop working was discussed among the workers．
I have no idea whether he is there．
4、引导主语从句时，只能用whether。
Whether he comes or not doesn't concern me．
5、引导表语从句时，只能用whether。
What Maria doesn't know is whether there will be enough snow．
四、if可引导条件状语从句，译作“如果”，whether可引导让步状语从句，译作“不管、无论”。
If I were you，I would not buy．
Whether he agrees or not，I shall go there．
巧记whether与if异同讲课稿
巧记w h e t h e r与i f 异同
巧记whether与if异同 主从表从同位从，if不用whether用； discuss和介词后，whether引宾从； 不定式、or not后在跟，whether独能显神通； 宾从若是否定句，if发挥其功用； 避免歧义要慎重，其他情况可换用。 一、引导主语从句，常用whether． (1)Whether the meeting will be held is uncertain．会议是否召开还不能确定． (2)It is unknown whether he will come．他是否来还不知道。 3.Whether we’ll go camping depends on the weather. 二、引导表语从句常用whether (1).The question is whether he can finish the work by the end of this week． 问题是到这周末他是否能完成这个工作。 (2).What we want to know is whether he will come to speak to us． 我们想知道的是他能否来给我们讲话。 3.The question is whether it is worth doing. 三、引导同位语从句，常用whether. (1).The question whether he will come is important．他是否来这个问题很重要。 (2).The plan whether we’ll go outing tomorrow hasn’t been made．明天我们是否郊游这个计划还没订。 (3).The question whether we need it has not been decided. 四、引导宾语从句。引导及物动词的宾语从句，用whether, if皆可； 介词的宾语从句，一般只用whether引导；
by的用法总结
by的用法小结： 1、介词prep. 在…旁；靠近 · Our teacher was sitting by the window. 我们的老师正坐在窗户旁边。 · Stand by me! 站到我的身旁来！ · We spent our holiday by the sea. 我们在海边度假。 2、介词prep. 经过 · He walked by me without speaking. 他走过我的身旁，没有说话。 · My brother goes by the building every day. 我弟弟每天从这楼旁走过。 3、介词prep. 用；靠；通过 using (showing who or what did something) · I know it by heart. 我把它记在心头。 · They can read by touch. 他们可以通过手摸来阅读。 · By getting up early, I can have an hour for reading English in the morning. 靠起得早，我每天早晨有一小时时间阅读英语。 4、介词prep. 不迟于 not later than · I shall be back by 5 o'clock. 最迟五点我一定回来。 · How many English parties had you had by the end of last term? 到上学期末，你们举行了几次英语晚会？ 5、介词prep. 通过；沿着 through; along; over
· We came through the fields, not by the road. 我们是穿过田野而不是沿那条路来的。· to send a letter by post 通过邮局寄信 6、介词prep. （表示作者）被；由 word that shows the author, painter, etc. · Thirty divided by two is fifteen. 三十除以二得十五。 · The child was saved by a PLA man. 这孩子是由一位解放军战士救活的。 · This bridge was built by the soldiers. 这座桥是士兵们造的。 7、介词prep. （指交通等）乘；用 word that shows what kind of transport, etc. · The man came by bus. 那人是坐公共汽车来的。 · They went to Shanghai by air. 他们坐飞机去上海。 8、介词prep. 在…情况下；在…时间during · Do you prefer travelling by day or by night? 你喜欢在白天还是在夜晚旅行？ 9、介词prep. （表示部分）在…部位word that shows which part · She led the child by the hand. 她拉着孩子的手往前走。 10、副词adv. 在旁边
as well as的用法
as well as的用法 曲靖市第二中学 as well as后接动词到底该用什么形式，这是一比较复杂的问题，归纳起来有以下几点值得注意： 一、as well as构成同级比较结构，意为“和…… 一样好”。 第一个as是副词，第二个as是连词，引导一个状语从句，表示同级比较。 在否定句中可用not so well as代替not as well as。 He speaks English as well as a native speaker. 他讲的英语是和英语是母语的人一样好。 He can operate the machine as well as I do. 他操作这台机器和我一样熟练。 He speaks English as well as she. 他说英语说得跟她一样好。 She plays every bit as well as the men. 她打得一点不比男人们差。 He doesn’t play half so well as his sister. 他演奏的水平不及他姐姐的一半。 He sings as well as, if not better than, Mary. 他要是唱歌不比玛丽唱得更好，但至少也是一样好。 She cooks as well as her mother (does). 她烧菜和妈妈一样好。 二、as well as用作连词，连接两个并列的同等成分，其意义为“不但……而且……”，“既……又……”，这时相当于not only ... but also ...。 它所连接的部分既可以是单词、短语，也可以是句子。 在A as well as B的结构里，语意的重点在A，不在B。翻译时要特别注意。The girl is lively as well as healthy.（连接两个表语）这女孩既健康又漂亮。 He can speak Spanish as well as English. (连接两个宾语) 他不但会说英语，而且会讲西班牙语。 In China, as well as in Canada, the weather changes from season to season. (连接两个状语) 中国的天气和加拿大一样随季节的变化而变化。 The teacher as well as the students enjoys listening to English songs.（连接两个主语）老师和学生都爱听英语歌曲。 He grows flowers as well as vegetables. 他既种菜也种花。 She shares (in) my troubles as well as my joys. 她与我同甘共苦。 They have a flat in town as well as in the Country. 他们在城里有一套公寓，在乡村还有一所房子。 We are repairing the roof, as well as painting the walls. 我们既油漆墙壁，又修房顶。 It is important for you as well as for me. 这对我很重要，对你也很重要。 Lily as well as her parents is very fond of classical music. 不但莉莉的父母，而且连
whether和if的用法区别
whether和if的用法区别 whether与if作“是否”讲，在用法上有相同之处，也有不同之处。 一、相同之处。 和if都能引导宾语从句，常置于see,ask,learn,tell,wonder,doubt,find out等动词之后。 如：He asked me whether/is I could help him. I want to know whether/if he lives there. 和if都可用it作形式主语从句中。如：it's uncertain whether/if he'll come this evening. 3.在be uncertain/doubtful之后，常用whether引导宾语从句，有时也可以用if，如：We are uncertain whether/if Mary will come. 二、不同之处。 可置于句首引导主语从句，而if不能。如：___the 2000 Olympic Games will be in Beijing is not known yet. 答案是C。 可用在介词之后，引导宾语从句，而If则不能。如：Success depends on whether we make evough effort. 可引导表语从句，if则不能。如：The puestion is whether it is not worth doing. 4.在名词之后引导同位语从句时，用whether而不用if。如：The question whether the students answered correctly should be decided by the teacher. 后可接不定式，而if不能。如：Please tell us whether to go or stay here. 6.在有些动词（如discuss）之后，只能用whether，而不用if引导宾语从句。如：We discussed whether we should close the shop. 7.在引导否定概念in宾语从句时，只能用if，而不用whether.如：he asked me if I hadn't finished my work. 英语时态一般现在时表示现在、经常或习惯的动作或状态和普遍现象、常识或客观真理；一般过去时用于过去某一时间内发生的或过去习惯性的动作或状态；一般将来时表示将要发生的动作或存在的状态，将来打算做的事情；现在完成时表示过去发生的动作造成目前的结果和对现在造成的影响或表示从过去延续至今的动作、状态和习惯等；将来完成时表示将来某时之前业已完成或发生的事情；过去完成时表示过去某时间之前已经发生的动作或状况，即过去的过去。注意每一种时态与其他时态的交叉使用情况。英语共有十六种时态，其表现形式如下(以study为例)： 一般时进行时完成时完成进行时 study studies am studying is studying are studying have studied has studied have been studying has been studying studied was studying were studying had studied had been studying shall study will study shall be studying will be studying shall have studied shall have been studying will have been studying should study would study should be studying would be studying should have studied would have studied should have been studying would have been studying 但考试中出现的一般有以下几种。 第一节一般现在时 一、表示一般性或经常发生的动作或状态 二、表示习惯性动作和状态或普遍的现象或常识 三、表示客观事实、客观规律和客观真理。在宾语从句中，即使主句的谓语动词用了过去时，只要从句表示的是客观真理，从句的谓语动词也要用一般现在时 四、祈使句必须用动词原形，其否定结构用“don`t＋动词原形”，如：Go and fetch some water. ／Don`t do that. 五、在反义疑问句中，如果主句用肯定句，那么，反问句用否定形式；如果主句用否定形式，那么，反问句就用肯定形式。而且前后在时态上要一致。但祈使疑问句用won`t you进行反问。如：See a film tonight, won`t you？ 注：①祈使句后边可用附加疑问句，以加强语气。如果祈使句用肯定形式，附加疑问句用否定形式；如果祈使句用否定形式，附加句用肯定形式；如：Come here next Sunday, won`t you ／Don`t tell it to anyone, will you ②但如果祈使句的前一句有了表示强烈肯定的语言环境，即使祈使句用了肯定形式，其附加成分也可以用“will you”(表示肯定，如
IF的用法
IF的用法 if是英语中出现频率很高的连词，并且它的用法也很多。学生感到很难掌握，为了让同学们更多更好地了解其用法及其语法功能。现结合教学中遇到的情况，予以归纳，以供参考。 一、if作为连词，引导条件状语从句，它表示的意思是“假如”“如果”等。在复合句中如果主句用将 来时，则if引导的状语从句用一般现在时。例如： 1. If itdoesn’train, we will go to the park next Sunday. 如果天不下雨，下周星期天我们将去公园。 2. If you ask him，he will help you．如果你求他，他将会帮助你。 二、if还可以引导让步状语从句。这时if当作“即使是”，“虽说”解。例如： 1. If she’s poor，at least she’s honest．虽说她很穷，但至少她还是诚实的。 2. If I am wrong，you are wrong，too．即使说我错了，那么你也不对。 3. I’ll do it, even if it takes me all the afternoon．虽然会花费我一下午的时间，我还是要做这事。 三、if作为连词还可以引导宾语从句。引导宾语从句时和whether意思相同。例如： 1. Lily asked if ／whether she liked it. 莉莉问她是否喜欢它。 2. She asked if ／whether they had a cotton one．她问是否他们有一件棉织的。 四、if引导时间状语从句，当if做“当”或“无论何时”解而不含有条件之义时，if从句中的时态与主句中的时态相同。例如： 1. If youmix yellow and blue，you get green．你将黄色与蓝色混合，便会得到绿色。 2. If she wants the servant，she rings the bell．每当她需要仆人时，她便按铃。 五、if后接否定动词，用于感叹句中，表示沮丧、惊奇等。例如： I. Well，if I haven’t left my false teeth at home!真倒霉，我把假牙丢在家里了! 2. And if he didn’t try to kn ock me down!(What do you think he did!He tried knock me down!)你猜他想做什么?他想把我撞倒! 六、用于虚拟语气中，if从句中用过去式，表示不可能实现，大概不会实现或提出作为考虑的假定条件。例如： 1. If you were a bird, you could fly.假使你是只鸟，你便会飞了。 2. If I asked him(if I were to ask him) for a loan，would he agree?如果我向他借贷，他会答应吗? 另外，if从句中用过去完成式，表示过去未实现的条件(例如由于不可能实现或某人之未能实行)。例如： 1. If they had startedearlier，they would have arrivedin time．要是他们早些动身，他们便可及时到达了。 2. If they had not started when they did，they would not be here now．如果他们那时不动身，现在他们就不会在此地了。 第三，在文学体栽中，if有时可省略，然后将主语与所用的限定动词(尤其是were，had，should)倒置。例如： 1. Should it (=if it should)be necessary，I will go. 倘若有必要，我会去的。 2. Were I(=if I were) in your place，I would do the same ．如果我处于你的位置，我也会这样干的。 3. Had I(=if I had)known earlier，I would come．如果我早一点知道，我就会来。 七、if与其它一些介词的连用。
(完整版)time的用法总结
一. time的短语 from time to time 有时 on time 准时寸,in time 及时寸; all the time 始终，一直; at the same time 同时, ahead of time 提前 at no time 绝不 some time 一段时间 sometime在某一时候”可用来指过去或将来 sometimes （at times, from time to time）有时，不时” at a time （a time）
at one time （once） at times ( sometimes) in no time (immediately ) 立刻，马上; have a good/nice time (enjoy on eself) 过的愉快 for the time being 暂时” “ Many a time/many times 多次 take one ' s time容 kill time消磨时间 【活学活用】选出与画线部分意思相同或相近的选项 1. Jim comes to visit us from time to time. That' always the happiest time for the family. A. on time B. sometime
C. at times D. some times 2．At no time ______ study though __ ___great progress. A. should we give up; we have made B. shouldn 'w t e give up; we have made C. we should give up; we have made D. we shouldn 'g t ive up; have we made 3. ---When shall we visit the Science Museum?” --- ________ next week. ” A. Sometime B. Sometimes C. Some time D. Sometimes 答案：1. C2.A 3A 二．time 相关从属连词高考常考点 1. every time / each time 每次Every time I call on him, he is out.
as...as...的用法总结
as...as...的用法总结 as...as...的用法其实很简单，快来一起学习吧。下面就和大家分享，来欣赏一下吧。 as...as...的用法其实很简单 as是英语中用得比较多的一个词，也是很多小伙伴反映较难掌握的一个词。as的词性较多，用法也较复杂，我们今天先讲一下很常用的as...as...的用法 as...as...的基本意思为“与……一样”，"像...一样的"。例如： The tree is as tall as the building(is). 这棵树和那栋楼一样高。 其中的第一个as为副词，其后通常接形容词或副词(用原级) ，第二个as可用作连词(后接从句)。 as...as...的用法 1 基本用法： 虽然都是as...as...但在不同的语境下，意思也不同。例如：
1.表示不同人或物同一性质的比较，意为“……和……一样……" Michael is as bright as George(is). 迈克尔和乔治一样聪明。 2. 表示同一个人或物不同性质的比较，意为“既……又……” Alice works as happily as(she)plays(happily). 艾丽丝愉快地工作，尽情地玩。 3. 用于表示两个人或物不同性质的比较，表示程度相同或相当，意为“……且/而……”。 He was as handsome as his wife was beautiful. 他长得非常英俊，他的妻子也长得非常漂亮。 He was as experienced as his brother was green. 他经验丰富，而他兄弟却涉世未深。 使用时应注意以下几点： 1. 在否定句中，第一个as 也可换成so： He doesn’t study as [so] hard as his brother. 他学习不如他弟弟努力。 2. 在该结构的两个as之间通常接形容词或副词的原级，但若涉及数量或程度，可用“as much+不可数名词+as”和“as many+可数名词复数+as” ：
英语中if的用法
精心整理1.(表示条件)如果,主句用将来时，if从句用现在时表示将来Hewillcomeifyouinvitehim. 如果你请他,他会来的。 2.(表示虚拟)假如,要是 1 a. b. 句型：条件从句主句 过去完成时should(would)have+过去分词 Ifshehadworkedharder,shewouldhavesucceeded. Thericewouldnothavebeenburntifyouhadbeenmorecareful.
IfmylawyerhadbeenherelastSaturday,hewouldhavepreventedmefromgoing. Ifhehadcomeyesterday,Ishould/wouldhavetoldhimaboutit. 含义：Hedidnotcomeyesterday,soIdidnottellhimaboutit. c. were+ Ifyousucceeded,everythingwouldbeallright. Ifyoushouldsucceed,everythingwouldbeallright. Ifyouweretosucceed,everythingwouldbeallright.
3.是否=whether连接宾语从句 Iwonderifsheisill. 不知她是否病了。 连接词conj. 1.( 2.( 3.( 4.是否 不知她是否病了。 5.(表示因果关系)每一次...的时候(总是会) IfIfeelanydoubt,Iinquire. 我一感到有疑问就随时询问。 if作为连词的时候，一般用于条件状语从句或者是宾语从句或让步状语从句
If和+whether的用法讲课教案
If和whether if不能替换whether的5种情况 1.正式文体中，句中有or not 时 2.引起主语，表语，同位语从句时 3.作介词宾语时 4.放不定式前，与不定式组成词组时 5.作discuss等词的宾语时 以上是if和whether表示"是否"之意的区别，此外，if还有加入的意思，引起条件状语从句；而whether 另有不管无论之意，引起让步状语从句 whether与if作“是否”讲，在用法上有相同之处，也有不同之处。 一、相同之处。 1.whether和if都能引导宾语从句，常置于see,ask,learn,tell,wonder,doubt,find out等动词之后。 如：He asked me whether/is I could help him. I want to know whether/if he lives there. 2.whether和if都可用it作形式主语从句中。如：it's uncertain whether/if he'll come this evening. 3.在be uncertain/doubtful之后，常用whether引导宾语从句，有时也可以用if，如：We are uncertain whether/if Mary will come. 二、不同之处。 1.whether可置于句首引导主语从句，而if不能。如：___the 2000 Olympic Games will be in Beijing is not known yet. A.whether B.If C.Whether D.That 答案是C。 2.whether可用在介词之后，引导宾语从句，而If则不能。如：Success depends on whether we make evough effort. 3.whether可引导表语从句，if则不能。如：The puestion is whether it is not worthdoing. 4.在名词之后引导同位语从句时，用whether而不用if。如：The puestion whether the students answered correctly should be decided by the teacher. 5.whether后可接不定式，而if不能。如：Please tell us whether to go or stay here. 6.在有些动词（如discuss）之后，只能用whether，而不用if引导宾语从句。如：We discussed whether we should close the shop. 7.在引导否定概念in宾语从句时，只能用if，而不用whether.如：he asked me if I hadn't finished my work. whether和if都可以引导宾语从句，表示“是否”，在口语或间接引语中两者可以互换使用。如： I wonder if / whether I can get some advice from you. Ask him whether / if he can come. 但在有些情况下，whether和if的用法有一定区别。 1. whether引导的从句常可以与连词or或or not直接连用，而if一般不能。如： 正：Let me know whether you can come or not. 误：Let me know if you can come or not. 2. 当宾语从句提到句首时，只能用whether引导，而不能用if。如： 正：Whether it is true or not, I can’t tell. 误：If it is true or not, I can’t tell. 3. whether可以引导带to的不定式，if则不能。如： 正：I don’t know whether to accept or refuse.
with用法小结
with用法小结 一、with表拥有某物 Mary married a man with a lot of money . 马莉嫁给了一个有着很多钱的男人。 I often dream of a big house with a nice garden . 我经常梦想有一个带花园的大房子。 The old man lived with a little dog on the lonely island . 这个老人和一条小狗住在荒岛上。 二、with表用某种工具或手段 I cut the apple with a sharp knife . 我用一把锋利的刀削平果。 Tom drew the picture with a pencil . 汤母用铅笔画画。 三、with表人与人之间的协同关系 make friends with sb talk with sb quarrel with sb struggle with sb fight with sb play with sb work with sb cooperate with sb I have been friends with Tom for ten years since we worked with each other, and I have never quarreled with him . 自从我们一起工作以来，我和汤姆已经是十年的朋友了，我们从没有吵过架。 四、with 表原因或理由 John was in bed with high fever . 约翰因发烧卧床。 He jumped up with joy . 他因高兴跳起来。 Father is often excited with wine . 父亲常因白酒变的兴奋。 五、with 表“带来”，或“带有,具有”，在…身上，在…身边之意
if用法归纳
1. If you eat my food, I won’t talk to you. (P58) 2. I will die , I don’t have food, (P58) 3. What shall we do if it rains tomorrow? 5. She asked me if I was fond of music. 她问我是否喜欢音乐。 6. Can you tell me if they’re planning to come? 你能告诉我他们是否打算过来吗？ 7. I don’t know if she’s coming. 我不知道她是否会来。 ◇相关词组 ☆if you want/like如果你愿意的话 You can come and stay with us if you want. ☆if so如果是的话 Are you planning to return to work, and if so, who is going to look after the baby? ☆if not如果不是的话 Has anyone dealt with the technical problems? And if not, why not?☆if necessary/if possible 如果必要/可能的话 We are ready to fight for our rights if necessary. I should like to be back here by 10:30 if possible. ☆even if即使 I’d rather never sell this painting, even if they offered me a million dollars. ☆what if 要是……，那怎么办？如果……那会怎样？ What if the boss walked in here now and saw us? ☆as if好像是…… She always talks to me as if she was my sister. ◇相关练习 动词填空： 1. If it ______ (be) sunny tomorrow, I ______( walk) to school . 2. We ________ (not have ) our sports meeting if the
if与whether用法区别
if与whether用法区别 收集整理：王俊尧 1.下列情况只能用whether： （1）直接与or not连用时,往往用whether(if…or not也可以使用)。如: Let me know whether or not he will come. (= Let me know whether / if he will come or not.) 让我知道他是否能来。 I don't know whether or not he does any washing. (= I don't know whether / if he does any washing or not.) 我不知道他在家洗不洗衣服。 I wonder whether we stay or whether we go. 我想知道我们是去还是留。 (2) 在介词之后用whether。如： I'm interested in whether he likes English． 我关心的是他是否喜欢英语。 We're thinking about whether we can finish the work on time． 我们正在考虑是否能按时完成这项工作。 I worry about whether I hurt her feelings． 我担心是否伤了她的感情。 (３)在不定式前用whether。如： He hasn't decided whether to visit the old man． 他尚未决定是否拜访那位老人。 I don't know whether to go．我不知去否。 He hasn't decided whether to go by bus or by train． 他还未决定是乘公共汽车去还是坐火车去。 （４）whether置于句首时，不能换用if。如： Whether this is true or not，I can't say． 这是否真的我说不上来。 （５）引导主语从句和表语从句时宜用whether。如： Whether she will come or not is still a question． 她是否能来还是个问题。 The question is whether we can catch the bus． 问题是我们能否赶上公共汽车。 （６）若用if会引起歧义时，则用whether。如：
to 用法总结
be/get/become used to 习惯于 be related to 与…有关系 be addicted to 沉溺于；对…上瘾 be opposed to 反对 devote oneself to献身于；专心于 be devoted to 致力于；忠诚于 be admitted to 被…录取；准进入 be reduced to 沦为 reduce…to…使…沦为 be attached to附属于；喜欢；依恋 be adjusted to 适应 be sentenced to被判处 be exposed to 暴露于；遭受 be/become/ get accustomed to//accustomed to 惯于；有…习惯be engaged to 与…订婚 get down to 着手做 lead to 导致 object to反对；不喜欢；不赞成 give rise to 引起 stick to 坚持； see to 负责；注意 contribute to对…作贡献；有助于 make contributions to对…作贡献 apply oneself to 致力于 in addition to除…之外 turn to转向；求助于 look up to 尊敬 belong to 属于 take to 喜爱；开始 respond to 回答；对…作出回应 amount to等于 refer to 谈到；参考；查阅 turn a blind eye to对…视而不见 turn a deaf ear to 对…充耳不闻 show honour to向…表示敬意 propose a toast to 提议…… set fire to 放火烧…… occur to sb. 想起；想到 hold to 坚持；抓住 help oneself to 随便用…… hold on to 抓住；固守
if、 whether 用法总结
whether,if if和whether通用，都表示“是否”的意思。一般来说，后者比较正式，在口语中前者常用来代替后者。但两者有时具有不同的暗示。用whether时，正反两面的选择意义较强，问话人并不在意回答是肯定还是否定；而用if时，则比较强调单方面，即正面，问话人希望得到肯定的回答。另外，还要注意以下几点： 一、whether和if都可以与or not连用；但写在一起时，只能用whether，不能用if。如： I don't care whether (或if) it will rain or not． I don't care whether or not it will rain. (不用if) 二、在引导宾语从句时，应注意： 1、表示“是否”时，两词都能引导宾语从句。 I wonder if/whether you can examine him now． 2、宾语从句移置句首时，用whether，不用if。
Whether it is true or not，I can't say． 3、宾语从句为否定形式时，通常用if，而不用whether。 I asked Tom if Mary wouldn’t come． 4、作discuss等词的宾语，用whether不用if。 We discussed whether we should buy the gift for him． 三、在下列情况下，只能用whether，不能用if。 1、与不定式连用时，只能用whether． He can't decide whether to accept or refuse． 2、在介词后，只能用whether。 Everything depends on whether he is ready． 3、在名词后作同位语时，只能用whether。
whether和if用法
1.whether和if均可用来引导主语从句，但if引导的从句不能位于句首。 如：Whether they win or lose is all the same to me. 他们是赢是输於我都一样.（此时whether不能换作if ） It's doubtful whether there'll be any seats left.说不上还有没有空座位了.(此句whether能换作if) 2.whether和if均可用来引导宾语从句。如： ①I don't know whether/if I will be able to come.我不知道我是否能来. ②She asked me whether/if I was interested in working for her.她问我是否有兴趣为她工作。 ③We'll be told tomorrow whether we should take the exam or not.我们明天才知道是不是应该参加考试. ④I asked him whether he had done all the work himself or whether he had had any assistance. 我问他这些工作都是他自己做的还是别人帮他做的. ( 注意: 在两个供选择的从句之间若用or字, 则须重复whether一字. ) 注:⑴当强调宾语从句并将其提前时只能用whether。 如:Whether I'll have time to go with you I am not sure.我很难说我们是否有时间跟你们一起去。 ⑵从句作介词宾语时只用whether不用if。 如:She was undecided about whether she should accept his offer. 她拿不定主意应该不应该接受他的好意 ⑶当whether和or not连用时，只用whether不用if。当or not放在whether引导的从句句尾，则可以用if来替换。 如: I don’t know whether or not he will come.我不知道他是不是回来。 I'll be happy whether/if I get the job or not我能不能得到那份工作都一样高兴 ⑷当whether和or 连用表示明确的选择时，只用whether不用if。 如:He asked me whether I wanted to go there by train or by bus. 他问我是想乘火车还是坐公共汽车去那里。 He hesitated about whether he should drive or take the train.他开车去还是坐火车去, 犹豫不决注:whether 和or 连用还可以引导让步状语从句,此时也不用if。 如：We'll go on with the work, whether we can find the necessary tools or not. 不管我们能否找到所需的工具,我们要把这件工作做下去。 Whether or not it rains / Whether it rains or not, we're playing football on Saturday. 无论下不下雨, 我们星期六一定踢足球. ⑸动词discuss，decide,consider等后习惯上也常用Whether引导从句，不用if。 They discussed whether they should leave at once.他们讨论了是否应该马上离开。We discussed whether the house should be sold. 我们讨论了这房子是否应卖掉。 3.表语从句用whether引导不用if. 如:①The doubt was whether you had broken the beautiful vase. 疑问是你是否打坏了这只漂亮的花瓶。 4.同位语从句用whether引导不用if. 如:①The question whether we'll build another lecture building hasn't been settled. 是否要另建一幢教学楼的问题还未决定。 5. 在动词不定式之前，只能用whether，不能用if。 如:①The question is whether to go to Munich or Vienna. 问题是去慕尼黑还是去维也纳. ②She doesn't knows whether to get married now or wait. 是否现在结婚或是等待她不知道。 ③We were wondering whether to go today or tomorrow. 我们弄不清是今天走还是明天走. ④I'm not sure whether to resign or stay on. 我拿不准主意是辞职还是留任. Answers: BADDC ABCAB ABADD B