八年级下册语法知识重点.doc

八年级下册语法知识重点1. If 引导的条件状语从句（1） 当主句和从句所表示的是原理、客观事实、规则时，主句是一般现在时（包括祈使句和含有情态动词can，may，must等），从句也用一般现在时。e.g.1.You must see the doctor if you are ill.如果你生病了，你就必须去看医生。（含情态动词）2. If you stick a pin into a balloon , it bursts.如果你用针刺气球，它就会爆炸。（原理）3. Be careful if you cross the road.如果你过马路，请小心。（祈使句）（2） 在if引导的条件状语从句中，如果从句谈论的时一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。e.g.1.If it rains tomorrow, we will not go to the zoo.2. If you go to bed earlier, you wont feel tired in the morning.2. 后带ing和do的动词seeSee sb do sth看到某人经常做某事或做某事的全过程See sb doing sth看到某人正在做某事noticeNotice sb do sth 注意到某人经常做某事或做某事的全过程Notice sb doing sth注意到某人正在做某事watchWatch sb do sth观察到某人经常做某事或做某事的全过程Watch sb doing sth观察到某人正在做某事hearHear sb do sth听到某人经常做某事或做某事的全过程Hear sb doing sth 听到某人正在做某事listen toListen to sb do sth听见某人经常做某事或做某事的全过程Listen to sb doing sth 听见某人正在做某事3. 情态动词Should1、 作为情态动词，通常用来表示现在或将来的责任或义务，表示“应该，应当”。e.g.Crimeshouldbepunished.犯罪应受惩罚。二、作为情态动词，可以用来表示有较大可能实现的猜测、推论，表示“可能，该(=willprobably)”。e.g.Theheadmastershouldarrivesoon.校长可能很快就到了。 Theyshouldbehomebynow，Ithink.我想现在他们总该到家了吧。Exercise: 情态动词练习题 1. Jean _have kept his promise.I wonder why he changed his idea.A.must B.should C. need D.would2.-Could I use your bike?-Yes,surely you_.A.might B.will C.can D.should3.Its nearly eight o clock.Bruce_be here at any momentA.must B.need C.should D.can4.Tommy,you_play with the knife,you_get hurt.A.wont; cant B.mustnt; may C.shouldnt; must D.cant; shouldnt5.When he was there,he_go to that coffee shop at the corner after work every day.A.would B.should C.had better D.might6.-When can you get the film developed?I need it tomorrow morning.-It _be ready by 8：00.A.can B. should C.might D.need7.-Will you stay for another hour?-Sorry,_.One of my best friends is coming to see me.A.I mustnt B.I cant C.I neednt D.I wont8.Jason shouldnt_me your secret,but he meant no harm.A.have told B.tell C.be telling D.having told9.-Are you coming for dinner?-Im not quite sure.I_go to my uncles instead.A.must B.would C.should D.might10.-Dont forget to visit me when you come to Beijing.-_.A.I dont B.I wont C.I cant D.I havent11.He ought_have done so even though possible.A.not to B.to not C.not D.never12.Jane_have come to the party,but she _not find the exact time.A.could;could B.might;could C.should;could D.should;would13.So many mistakes in your homework!You_more careful.A.may be B.had to C.would be D.should have been14.Her brother_be at home now,because he was seen playing basketball in the stadium just now.A.mustnt B.neednt C.cant D.shouldnt15.-I cant understand why our boss is late.-He_the early bus.A.could miss B.may have missed C.can have missed D.might miss答案：1-5 BCCBA 6-10 BBADB 11-15 AADCB 4. 动词+介词/动词+副词动词+介词：构成的词组相当于一个及物动词，宾语总是在介词后面。e.g.I dont much care for the television. 我不是很喜欢电视。动词+副词：构成的词组可作及物动词，也可作不及物动词。作及物动词时，宾语的位置有两种情况：宾语如果是名词，则可放在副词后面，也可放在动词与副词之间；而如果宾主是代词，只能放在动词后面，即动词和副词之间。作不及物动词时，后不带任何名词或代词作宾语。e.g.Something unexpected has turned up.出现了令人意外的情况。5. 后带to do（动词不定式）的动词agree to do sth同意做某事decide to do sth决定做某事refuse to do sth拒绝做某事remember to do sth记得做某事forget to do sth忘记做某事try to do sth尽力做某事want to do sth 想要做某事6. Have to 与mustHave to 表示“不得不”，强调客观需要，有人称、时态和数的变化；而must则着重说明主观看法，表示个人的意志，是情态动词，没有人称、时态和数的变化。E.g.Did she have to pay a fine? 她非得交罚款吗？I must go there to help the poor.我必须去那儿帮助那些穷人们。（表示说话人自己的看法）在某些不需要强调这两种差别的场合，两者可以互换。e.g.I am afraid we have to / must leave now. 恐怕我们必须得走了。SummaryHave to must表示客观的需要说话人主观上的看法，主观上的必要有人称、数、时态的变化只有一种形式在否定结构中dont have to表示“不必”否定结构中，mustnt表禁止，neednt表示“不必”不能表示推测能表示推测，意为“一定是，肯定是”7. 词语辨析1 pay, spend, take, cost意义搭配payspendtakecost2 sometimes，some times，sometime与some timesometimes表示动作发生的不经常性，多与一般现在时连用some times其中time是可数名词，有来提问次数sometime表示某个不确切或不具体的时间，常用于过去时或将来时some time表“某一段时间”时，常常修饰延续性的动作3how often，how long，how soon 与 how many timeshow often“多久一次”，指动作的频率How often do you go to cinema?Twice a week.how long“（延续）多长时间 ”，回答用”for.”或”since.”引导的时间状语How long have you been in Amercia?For two years.how soon“还要多久（时间）才”，一般用将来时态，回答用”in.”引导的时间状语How soon will he be back?Hell be back in an hour.how many times“多少次”，用于询问次数，回答用once，twice，three times等How many times have you been here?Four times.e.g.1.How do you exercise?2. How does it take to get to Shanghai from here?3. How is the river?4. How is it from here to the park?5. How have you been here? 8. 状语从句在句中作状语的从句，分为九种，常见的有时间状语从句，原因状语从句，条件状语从句，结果状语从句及目的状语从句。1Until引导的时间状语从句Until意为“直到，在之前”。Until 和not.until的区别e.g.Continue in this direction until you see a sign. 一直朝着这个方向走，直到你看见一个指示牌。I didnt wake up until I heard the alarm clock. 直到听到闹钟响我才醒来。Summary: 2so that引导的目的状语从句So that是连词，意为“为的是，以便”。注意so that, in order that 和in order to的区别。So that/in order that后加从句，而in order to 后加短语。3unless引导的条件状语从句Unless是“除非，如果不”，相当于if.not。e.g.I wont go to the party unless Im invited. 除非我被邀请，否则我不会去参加晚会的。4as soon as引导的时间状语从句意为“一就”。e.g.He will report back here as soon as he arrives. 他一到达就会来这里汇报的。5so.that/such.that引导的结果状语从句句型中so是副词，常用来修饰形容词或副词，意思是“如此以至于”，常用句型为：主语+谓语+so+adj./adv/+that从句。Such.that句型中such是形容词，修饰名词，意思是“如此以至于”，常用句型为：A.主语+谓语+such+adj.+复数可数名词+that从句；B.主语+谓语+such+a(an)+adj.+单数可数名词+that从句；C.主语+谓语+such+adj.+不可数名词+that从句。由so.that引导的从句可转换成含不定式的简单句，即可转换为”.enough to.”或”too.to.”。He was so clever that he could understand what I said.He was clever enough to understand what I said.The question is so easy that I can work it out.The question is easy enough for me to work out.The bag is so heavy that she cant move it.The bag is too heavy for her to move.The girl is so young so that she cant dress herself.The girl is too young to dress herself.9. 过去进行时与when/while引导的时间状语从句When 当的时候 while 在期间 before 在之前After 在之后 as 当的时候 since 自从Until 直到过去进行时结构Was/were+V-ing时间状语用法表示过去某一时刻用某一阶段正在发生的动作What were you doing this time yesterday?表示某个短暂性动作发生的背景(主句动作和从句动作都发生在过去，动作时间长的用过去进行时，短的用一般过去时。）Jim hurt his hand when he was cooking.I met Diana while I was shopping this moring.表示两个同时持续的动作I was doing homework while he was listening to music从句区别When引导的时间状语从句：While引导的时间状语从句：10. 感叹句whatWhat+a/an+adj+可数名词单数（+主语+谓语）What+adj+可数名词复数（+主语+谓语）W