3-6年级英语 基本语法练习题
- 格式:doc
- 大小:39.00 KB
- 文档页数:4
六年级英语语法练习题40题(答案解析)1.There are many _____ in the classroom.A.studentB.studentsC.student'sD.students'答案解析:B。
选项A“student”是单数形式,题目中“many”表明要用复数形式,所以 A 错误。
选项C“student's”是所有格形式,表示“学生的”,不符合题意,错误。
选项D“students'”也是所有格形式,错误。
选项B“students”是复数形式,符合题意。
本题考查名词复数形式。
2.This is my _____ book.A.sisterB.sister'sC.sistersD.sisters'答案解析:B。
选项A“sister”是“姐妹”的意思,不是所有格形式,错误。
选项C“sisters”是复数形式,不是所有格形式,错误。
选项D“sisters'”是复数的所有格形式,而题目中是“my sister”的所有格,应该用单数所有格形式,错误。
选项B“sister's”是单数所有格形式,符合题意。
本题考查名词所有格形式。
3.The _____ are playing on the playground.A.childB.childsC.childrenD.childrens答案解析:C。
选项A“child”是单数形式,题目中“are playing”表明要用复数形式,所以 A 错误。
选项B 形式错误,child 的复数是children。
选项D 形式错误,children 本身就是复数形式,不能再加s。
选项C“children”是复数形式,符合题意。
本题考查名词复数形式。
4.That is _____ desk.A.TomB.Tom'sC.TomsD.Toms'答案解析:B。
选项A“Tom”是人名,不是所有格形式,错误。
小学生必须掌握的语法练习题语法是语言的基础,掌握良好的语法对于小学生的学习和成长至关重要。
通过语法练习题的训练,小学生可以提高语法意识和语言表达能力。
本文精选了一些常见的语法练习题,旨在帮助小学生巩固语法知识,提升语言运用能力。
一、词组搭配将下列句子中的空格处填上合适的词组。
1. I ________ my homework before dinner. (finish, for, do)2. Michael ________ his friend to the party. (brings, brought, bring)3. The cat ________ on the chair. (lie, lays, lays down)4. We often ________ puzzles on weekends. (do, make, play)5. Lucy ________ to the music with her friends. (sing, sang, is singing)二、时态练习根据句子的上下文,选择合适的时态填空。
1. It ________ (rain) heavily yesterday, so we ________ (stay) at home.2. He ________ (watch) a movie at this time yesterday.3. Sarah ________ (visit) her grandparents last weekend.4. They ________ (play) basketball every Saturday afternoon.5. I ________ (read) an interesting book now.三、句型转换将下列句子进行句型转换,每空一词。
1. He goes to school by bus. (改为否定句)He ________ ________ to school by bus.2. They have finished their homework already. (改为一般疑问句) ________ they ________ their homework already?3. Jenny is playing the piano in the living room. (改为一般疑问句) ________ Jenny ________ the piano in the living room?4. She is going to buy a new dress. (改为否定句)She ________ ________ to buy a new dress.5. Tom can swim very well. (改为一般疑问句)________ Tom ________ swim very well?四、动词的正确形式根据句子意思,填入动词的正确形式。
小学六年级英语语法基础练习题小学六年级的学生已经掌握了一定的英语基础,现在可以通过一些练习题来巩固和提高英语语法能力。
以下是一些适合小学六年级学生的英语语法基础练习题:1. 名词复数形式:- 写出下列名词的复数形式。
- Child: ________- Foot: ________- Leaf: ________- Mouse: ________2. 动词的时态:- 用正确的时态填空。
- I _______ (go) to the park yesterday.- She _______ (be) a teacher since 2010.- They _______ (not watch) TV now.3. 形容词和副词的比较级和最高级:- 将下列形容词转换为比较级和最高级。
- Big: ________, ________- Happy: ________, ________- Fast: ________, ________4. 代词的使用:- 用适当的代词填空。
- This is _______ (he) book. It's not _______ (I).- _______ (they) are my friends. _______ (we) are in thesame class.5. 介词的使用:- 用适当的介词填空。
- The cat is _______ the box.- The children are _______ the playground.- The books are _______ the shelf.6. 连词的使用:- 用适当的连词填空。
- I will go to the store, _______ I need to buy some milk.- She can play the piano, _______ she can also sing.7. 疑问句的构成:- 将下列陈述句转换为一般疑问句,并给出肯定和否定回答。
小学英语语法练习题及答案一、单项选择题1. — ______ does your father go to work?— He goes to work by car.A. HowB. WhenC. WhereD. Why2. My friend and I _______ to the park last Sunday.A. goB. wentC. goesD. is going3. _______ two pencils on the desk.A. There'sB. ThereC. They'reD. Here4. Helen ________ carrots and tomatoes for dinner.A. likeB. likesC. is likingD. liked5. _______ any milk in the fridge?A. There isB. Is thereC. There areD. Are there二、完形填空题John and Lisa are brother and sister. They are from the United States. They 1 a small garden. 2 garden is behind their house. In the garden, there 3 a big tree, some flowers, and a pond. Every 4 John and Lisa play in their garden. They 5 a lot of fun there.One day, they saw 6 small bird near the pond with a broken wing. The bird 7 fly away. John and Lisa 8 the bird and put it in a small box. They gave the bird some food and water. They wanted 9 bird to get better.Every day, John and Lisa took care of the bird. They talked 10 it and sang songs to it. After a few weeks, the bird's wing 11 better. It was 12 to fly again. John and Lisa opened the box and the bird flew away happily.John and Lisa were very happy 13 they helped a little bird. They loved animals and wanted to take care 14 them. They knew that everyone could 15 a small part to make the world a better place.1. A. has B. have C. had D. having2. A. Their B. They C. Them D. Theirs3. A. are B. is C. was D. were4. A. day B. night C. week D. morning5. A. is having B. has C. have D. had6. A. the B. a C. an D. and7. A. can't B. couldn't C. can D. could8. A. took care of B. took care C. take care of D. are taking care of9. A. a B. an C. the D. /10. A. to B. about C. with D. on11. A. gets B. got C. get D. getting12. A. able B. not able C. couldn't D. can't13. A. if B. because C. when D. while14. A. from B. for C. about D. of15. A. do B. did C. does D. doing三、阅读理解题ADear Sarah,How are you? I hope you are doing well. I am writing to tell you about my trip to Beijing. Beijing is the capital city of China. It is a very big and beautiful city.I visited the Great Wall. It was amazing! The Great Wall is very long and old. We took many photos there. I also went to the Summer Palace. It is a big park with a lake. We took a boat on the lake. It was so much fun!The food in Beijing was delicious. I tried Peking duck. It was very tasty.I also bought some souvenirs for you. I hope you like them.I miss you a lot. Don't forget to write back and tell me about your summer vacation.Love,Amy1. Where did Amy go on her trip?A. ShanghaiB. BeijingC. Hong KongD. Guangzhou2. What did Amy think of the Great Wall?A. BeautifulB. BoringC. SmallD. New3. What did Amy do at the Summer Palace?A. Took a boat on the lakeB. Climbed a mountainC. Visited a museumD. Took many photos4. What did Amy eat in Beijing?A. RiceB. NoodlesC. Peking duckD. SushiBMy name is Tom. I am 11 years old. I live in London, England. I have two brothers and one sister. My brothers are older than me, and my sister is younger. We all go to the same school.My favorite subject in school is math. I like solving math problems. My least favorite subject is history. I think it's boring.In my free time, I like playing soccer with my friends. I am on the school soccer team. We practice every Tuesday and Thursday after school. We have matches on Saturdays.I also enjoy reading books. My favorite book is Harry Potter. I have read all the books in the series. I like the adventures of Harry and his friends.1. How old is Tom?A. 10B. 11C. 12D. 132. What is Tom's favorite subject in school?A. MathB. EnglishC. HistoryD. Science3. How often does Tom practice soccer with his team?A. Every dayB. Every Monday and WednesdayC. Every Tuesday and ThursdayD. Every Saturday4. What is Tom's favorite book?A. Alice in WonderlandB. Charlotte's WebC. Harry PotterD. Matilda答案:一、单项选择题:1. A 2. B 3. C 4. B 5. B二、完形填空题:1. B 2. A 3. B 4. A 5. C 6. C 7. B 8. A 9. A 10.B 11. B 12. A 13.C 14.D 15. A三、阅读理解题:A: 1. B 2. A 3. A 4. C B: 1. B 2. A 3. C 4. C。
六年级课程复习语法练习题一、选择题1. Please turn off the lights ______ leaving the room.A. whenB. whileC. sinceD. if2. My sister _______ to the supermarket and bought some fruits yesterday.A. goB. goesC. goingD. went3. Tim ________ a new bike as his birthday present next month.A. getsB. getC. gotD. getting4. The teacher asked us _________ in the library.A. not talkB. don't talkC. to not talkD. not to talk5. _______ you ever _______ to the Great Wall?A. Did, goneB. Have, goneC. Do, wentD. Have, been6. Could you please ________ the window? It's too hot in the room.A. openB. openedC. openingD. opens7. The children _________ basketball in the playground at the moment.A. playB. are playingC. playedD. plays8. Linda _________ her homework yet. She is still doing it.A. didn't finishB. hasn't finishedC. doesn't finishD. hasn't finish9. My father _________ in a hospital. He is a doctor.A. worksB. workC. workedD. working10. _______ he _______ to the park every Sunday?A. Do, goB. Does, goC. Do, goesD. Does, goes二、用括号内所给词的适当形式填空1. My brother ___________ (come) back from school at 4:30 yesterday.2. There ___________ (be) some milk in the fridge.3. Look! The babies ___________ (sleep) in the crib.4. They ___________ (not visit) the museum last week.5. Peter and I ___________ (have) lunch at the restaurant now.6. My sister often ___________ (watch) TV after dinner.7. Mary ___________ (not eat) any sweets last night.8. Yesterday, we ___________ (play) soccer in the park.9. The students ___________ (not study) English tomorrow.10. Tom and his friends ___________ (ride) their bikes in the park.三、按要求改写句子1. We can not go out when it rains. (改为反义疑问句)_______ _______ go out when it rains, _______ _______?2. Tony can swim well. (改为否定句)Tony _______ _______ well.3. The students are playing basketball in the gym. (改为一般疑问句) _______ the students _______ basketball in the gym?4. I have done my homework. (对划线部分提问)_______ _______ you _______?5. They will visit the museum tomorrow. (改为否定句)They _______ _______ to the museum tomorrow.四、根据中文提示翻译成英文句子1. 昨天我和我的朋友们一起踢足球。
语法专项练习一、+动词ing1. like + 动词ingHe likes ______________________. (做风筝)2.am is are + 动词ingHis hobby is ___________________. (拉小提琴)He is ______________________. (听音乐)They are __________________. (摘树叶)I am _______________________. (写作业)二、+动词原形1.can + 动词原形He can ______________________. (抓蝴蝶)Can she ______________________? (画画)2.Do Does Did + 动词原形Do you ______________________? (弹钢琴)Does she _____________________? (集邮)Did he _______________________? (拍照片)3.Let’s +动词原形 Let’s =Let usLet’s______________________. (去旅行)Let us_____________________. (远足)三、a an 的用法一般在 a e i o u的前面用an 但university的前面用a 如:a university student(一个大学生)____ ant ____ elephant _____ ice-cream ____ orange _____ uncle_____university student四、季节与天气变化__________ is _________and warm. ___________ is sunny and _________.___________ is windy and __________. ___________ is _________ and cold.练习:1.What are you doing? I___________________ in the kitchen.(洗碗)2.What is his hobby? He hobby is__________________.(集邮)3.What are they doing? They ____________(跑步)4.Look! Mike _________________in the study.(写作业)5.It’s 2 o’clock. We _______________________.(上英语课)6. Do you _______________ every morning? (做早操)7.Let’s _______________ together.(看电视)五、时态与注意点一般现在时:sometimes有时 often经常 usually 通常always总是 every day 每天Sometimes + 人 + usually + 动词原形或者动词加s es+every dayI You We They Mike and Sarah The elephants +动词原形He She It Mike The elephant +动词 s es动词s es 的方法:1.一般的动词直接加s2.以ch sh o结尾的单词加es,watch—watches catch—catches wash—washes go—goes do—does3.以辅音加y结尾的,把y改成i,再加es fly—flies empty—empties以元音加y结尾的,直接加s play—plays4. have—has现在实行时:now现在人 + am is are + 动词ing +now.am is are 固定搭配:I am You are He is She is We are They are It is Mike is Mike and Sarah areThe elephant is The elephants are动词+ing 方法:1.一般的动词直接加ing2.以e结尾的动词,去掉e再加ingmake—making use—using take—taking have—havingride—riding dive—diving write—writing dance—dancing3.双写加ingget—getting set—setting run—running swim—swimming put—putting一般将来时:next week 下周 tomorrow明天人+ am is are +going to +动词原形 +tomorrow一般过去时:last week 上周 yesterday昨天人+动词过去式+yesterday★清华大学★英语系测试:为中小学生英语量身定做. 官方网站:://qinghua.yeryy/清华大学英语教授研究组提供初一.二班安全教育主题班会教案安全在我心中主要内容:学习一些生命安全、交通安全、校园安全等知识。
新人教版小学英语(3—6年级重点句型及语法)三年级上册1、向别人问好应该说――A: Hello! (你好!) B: Hi! (你好!)2、问别人的名字应该说-A:What’s your name?你的名字是什么?B:My name’s Chen Jie. 我的名字是陈洁。
3、跟别人分开应该说――A: Bye.\ Good bye!(再见)B: See you.(再见) \ Goodbye.(再见)4、A: I have a pencil\ bag\ruler 我有一只铅笔\书包\尺子。
B: Me too . 我也有。
5、早上相见应该说-――A: Good morning. 早上好!B: Good morning! 早上好!6、下午相见应该说――A: Good afternoon! 下午好!B: Good afternoon! 下午好!7、跟新朋友第一次见面――A: Nice to meet you! 见到你很高兴。
B: Nice to meet you,too! 见到你也很高兴!8、A: Let’s go to school! 让我们一起去上学!B: OK! 好的。
9、看见久未见面的朋友或者别人身体不舒服,你该这么打招呼-A: How are you ? 你好吗?B: Fine,thank you我很好,谢谢你。
10、A: Let’s paint. 让我们画画。
B: Great! 棒极了!11、A: Look I have a rabbit\monkey. 看,我有一只兔子\猴子。
B: Cool\Super \ Great \ Wow! 酷\超级好\棒极了\好厉害.12、你想看下别人的东西,你该这么说――A: May I have a look? 我可以看一看吗?B: Sure. Here you are! 当然可以。
给你!13、请别人吃东西,你该这么说――A: Have some French fries. 吃一些炸薯条。
P E P小学英语语法要点及习题写出下列各词的复数 I( ) him( ) this ( )her ( ) watch( ) child ( ) photo ( ) diary( ) day( ) foot( ) book() dress() tooth( ) sheep( ) box( ) strawberry( ) peach( ) s a n d w i c h()m a n()w o m a n()?写出下列动词的第三人称单数 drink go stay make look ____ has___ pass ____??carry ____come_______?watch___ plant____ fly ____study_______ brush________ do_____??teach______用括号内动词的适当形式填空。
1. He often ________(have) dinner at home.2. Daniel and Tommy _______(be) in Class One.3. We __ watch_____(not watch) TV on Monday.4. Nick _______(not go) to the zoo on Sunday.5. ____ they ______(like) the World Cup?6. What ______they often _____(do) on Saturdays?7. _____ your parents ______(read) newspapers every day?8. The girl _____(teach) us English on Sundays.9. She and I _____(take) a walk together every evening.10. There _____(be) some water in the bottle.11. Mike ____(like) cooking.12. They ____(have) the same hobby.13. My aunt (look) after her baby carefully.14. You always _____(do) your homework well.15. I ____(be) ill. I’m staying in bed.16. She ____(go) to school from Monday to Friday.17. Liu Tao ___(do) not like PE.18. The child often _____(watch) TV in the evening.19. Su Hai and Su Yang ____(have) eight lessons this term.20. -What day ____(be) it today?-It’s Saturday.按照要求改写句子1. Daniel watches TV every evening.(改为否定句)2. Do you do your homework every day?(作肯定回答)3.Does she like milk? (作否定回答)4. Amy likes playing computer games? (改为一般疑问句)5.We go to school every morning.(改为否定句)6. He speaks English very well.(改为否定句)7.I often play football in the park. (对划线部分提问)8. John comes from Canada.(对划线部分提问)__________________________________________________ _9. She is always a good student.(改为一般疑问句,作否定回答)__________________________________________________ ______10. Simon and Daniel like going skating.(改为否定句) __________________________________________________ _改错(划出错误的地方,将正确的写在横线上)1. Is your brother speakEnglish? __________________2. Does he likes goingfishing? __________________3. He likes play games afterclass. __________________4.Mr. Wu teachs usEnglish. __________________ 5. She don’t do her homework on Sundays._________________写出下列动词的现在分词:play____ run_____ swim_____ make____ go______ like____ write____ski_____ read_____ have_____sing ___ dance____ put______ see_____ buy ______ love_____live______ take____ come ____ get_____stop_______ sit _____ begin_____ shop________用所给的动词的正确形式填空:1.The boy __________________ ( draw)a picture now.2. Listen .Some girls _______________ ( sing)in the classroom .3. My mother _________________ ( cook )some nice food now.4. What _____ you ______ ( do ) now?5. Look . They _______________( have) an English lesson .6.They ____________(not ,water) the flowers now.7.Look! the girls ________________(dance )in the classroom .8.What is our granddaughter doing? She_________(listen ) to music.9. It’s 5 o’clock now. We_____________(have)supper now10.______Helen____________(wash )clothes? Yes ,she is .句型转换:1. They are doing housework .(分别改成一般疑问句和否定句)__________________________________________________ ______________________________________________________ ____2.The students are cleaning the classroom . ( 改一般疑问句并作肯定和否定回答)__________________________________________________ _________________________________________________________ _______3.I’m playing the football in the playground .(对划线部分进行提问)__________________________________________________ ______4.Tom is reading books in his study . (对划线部分进行提问)__________________________________________________ _______填空。
小学英语语法总结与专项练习一、名词复数变化规则名词复数变化规则专项练习题二、一般现在时一般现在时的概念一般现在时的构成一般现在时的变化动词第三人称单数的变化规则专项练习题三、现在进行时现在进行时的概念现在进行时的构成现在进行时的变化动词ing形式的变化规则专项练习题四、一般将来时一般将来时的概念一般将来时的构成一般将来时的变化专项练习题五、就划线部分提问一、名词复数变化规则1.一般情况下,直接加-s,如:book-books,bag-bags,cat-cats,bed-beds 2.以s.x.sh.ch结尾,加-es,如:bus-buses,box-boxes,brush-brushes, watch-watches3.以“辅音字母+y”结尾,变y为i,再加-es,如:family-families, strawberry-strawberries4.以“f或fe”结尾,变f或fe为v,再加-es,如:knife-knives5.不规则名词复数:man-men,woman-women,policeman-policemen,policewoman-policewomen, mouse-mice,child-children,foot-feet,tooth-teeth,fish-fish,people-people,Chinese-Chinese,Japanese-Japanese名词复数专项练习I_________him_________this___________her______watch_______child_______photo________diary______day________foot________book_______dress________tooth_______sheep______box_______strawberry_____thief_______yo-yo______peach______sandwich______man______woman_______paper_______juice___________water________milk________rice__________tea__________二、一般现在时概念:1.表示事物或人物的特征、状态。
小学阶段基本语法练习题一、名词复数,请写出下列词的复数形式。
city _____ _zoo ______ country _________ tooth ________ mouse ________ boy________ room ________car ____ tree ______horse ______ bus__________ fox _____ baby _____ family _____ dish _____ radio _____ photo _____ piano _____ knife _____leaf _____ man _____ woman _____ child ___ foot ______ this ______dress_______ that________ watch_______ diary_______key______ day________ book________ sheep_______ tea___________box___________ strawberry_________peach__________ sandwich__________ paper_________ juice_______ water________milk__________ rice_______ people__________ deer____________二、填入所给名词的正确形式1. I have two____________ (knife)2. There are many ___________ here. (box)3. There are many _________ on the road. (bus)4. A few ________ are drawing on the wall. (boy)5. The __________ are playing football now. (child)6. Please take two _______________ for me. (photo)7. I like the red ________________.(tomato)8. Would you please clean your _____________ now? (tooth)9. Do you want some _________? (milk)10. There are ten __________ _________in our school. (woman teacher)三、把下列句子改为复数句子。
1. This is a red box. ___________________2. That is an old watch. ____________________3. It is a blue bus. _____________________4. He is a baby. _______________________四、写出下列动词的第三人称单数。
1. clean--2. go--3. have--4. do--5. play--6. fly—7. come-- 8. brush-- 9. watch-- 10. study-- 11. ask-- 12. answer—13. swim-- 14. catch-- 15. write-- 16. eat-- 17. make-- 18. paint—19. learn-- 20. phone-- 21. run-- 22. hop-- 23. sing-- 24. pick—25.drink_____26.stay_____27.look______28.pass_____29.carry____30.plant___ 31.teach_____五、用括号内动词的适当形式填空。
1.He often ________(have) dinner at home.2.We _______(not watch) TV on Monday.3.Nick _______(not go) to the zoo on Sunday.4.______ they ________(like) the World Cup?5.What _______they often _______(do) on Saturdays?6._______ your parents _______(read) newspapers every day?7.The girl _______(teach) us English on Sundays.8.She and I ________(take) a walk together every evening.9.There ________(be) some water in the bottle. 10.Mike _______(like) cooking.11.They _______(have) the same hobby. 12.My aunt _______(look) after her baby carefully.13.You always _______(do) your homework well. 14.I _______(be) ill. I’m staying in bed. 15.She _______(go) to school from Monday to Friday. 16.Liu Tao _______(do) not like PE.17.The child often _______(watch) TV in the evening.18.SuHai and SuYang _______(have) eight lessons this term.19 Mike’s sister ________ (cook) nice food. I _______ (like) eating it very much.20_______ (do) your father_______ (watch) TV in the evening? No, he_______ (not).21 Tom usually_______ (play) football after school22 He _______ (live) in a small town near Nanjing.23 I like_______ (cook) and_______ (grow) flowers.24 I ______ (go ) to school by bus, and he ______(go) to school by bike.25 Who ________ (sing) beautifully in your class? Jim.六、选出正确的答案:1. She (like / likes) to play football.2. He (like / likes) drinking milk.3. I (like / likes) to watch TV.4. We (like / likes) to play badminton.5. They (like / likes) to sing songs .6. She (read / reads) books every day.7. He (play / plays) computer games every day. 8. It (listen / listens) to the radio every day.9. Linda (draw / draws) pictures every day. 10. Jane and Linda (play / plays) football every day.七、把下列句子变为否定句:1. She draws pictures every day.2. We like playing football.3 Linda swims every day.4 They like playing games.5.My father reads newspaper in the evening.6. He likes drawing pictures .八、把下列句子变为疑问句,并做肯定回答。
1. My father can ride a horse.2. she does her homework at home3. Miss Green likes dancing very much.4. we clean the classroom.5. My mother cooks the meals.6. I clean the bedroom everyday.7.They read books in the classroom. 8. The children sing in the music room.九、写出下列动词的现在分词:go______ stand____ sleep________ eat_________ sing____________ drink___________ read__________look_______ walk_________watch__________draw____________ fly______ open______ jump______do_______paint____________ pick____________ play____________ talk________ cook________ learn________look____________ climb___________ clean___________ come___________ dance___________ close____________ make___________ ride____________ write____________ take____________ phone___________ move___________ have____________ sit_________ swim___________ run________ cut___________get____________ begin___________chat___________ stop__________ make__________like________ write________ sing ________ dance_________see________buy ________ love______ live_______十、用所给的动词的正确形式填空:1.The boy ______ ____________ ( draw) a picture now.2. Listen .Some girls ______ _________ ( sing) in the classroom .3. My mother ______ ___________ ( cook ) some nice food now.4. What _____ you ______ ( do ) now?5. Look . They ______ _________( have) an English lesson .6.They _____ _______(not ,water) the flowers now.7.Look! the girls ______ __________(dance ) in the classroom .8.What is our granddaughter doing? She ___ ______(listen ) to music.9. It’s 5 o’clock now. We ____ _________(have) supper now10.______Helen____________(wash ) clothes? Yes ,she is.十一、句型转换:1. They are doing housework. (分别改成一般疑问句和否定句) __________________________________________________________________________________________________________________________2.The students are cleaning the classroom . (改一般疑问句并作肯定和否定回答) ________________________________________________________________________________________________________________________________3.I’m playing the football in the playground . (对划线部分进行提问) ________________________________________________________________________________________________________________________________4.Tom is reading books in his study . (对划线部分进行提问) ________________________________________________________________________________________________________________________________十二、一般过去时练习题,单项选择:从下列各题后所给的四个选项中选择最佳答案填空。