外研版四年级英语上册词汇专项复习卷含答案
词汇专项复习卷时间：60分钟满分：100分一、根据图片补全单词。
(10分)1. 2. 3. 4.j____ice l____ ____ht f____c f____ow5. 6. 7.the S__r__ __g F__ __ti____ ____l s____ ____ ____ r____d____ab________e8. 9. 10.p____e____e________ c____o____k go s____ ____a____ght on 二、给单词选出相应的汉语意思并把序号写在题前的括号内。
(5分)()1. cinema A. 电影院 B. 房屋()2. want A. 划船 B. 想要()3. bread A. 灯 B. 面包()4. read A. 阅读 B. 书写()5. tomorrow A. 明天 B. 今天()6. horse A. 马 B. 羊()7. kid A. 小孩 B. 饼干()8. month A. 年 B. 月()9. run A. 跳 B. 跑()10. family A. 火车 B. 家庭三、选出不同类的单词。
(5分)()1. A. month B. day C. metre()2. A. Halloween B. Christmas C. family()3. A. jumping B. running C. help()4. A. tea B. drink C. milk()5. A. bus B. train C. afraid()6. A. people B. left C. right()7. A. beside B. next to C. supermarket()8. A. horse B. elephant C. face()9. A. three B. twelve C. station()10. A. school B. cinema C. clock四、按照要求写一写。
(16分)1. 写出三种食物____________________________________2. 写出三个动作____________________________________3. 写出三种动物____________________________________4. 写出三个地点____________________________________5. 写出四种交通工具_____________________________________________五、改变下列单词的首字母，使之成为所给汉语对应的单词。
(14分)1. take →__________制作2. coat→____________小船3. duck→__________运气4. right→____________灯5. live→____________给6. wish→____________钓鱼7. dark→__________公园8. come→__________一些9. near→__________熊10. winner→________晚餐11. look→__________书12. like→__________自行车13. rich→__________米饭14. ball→__________高的六、选出与下列图片相符的短语。
(10分)1. 2. 3. 4. 5.() () () () ()6. 7. 8. 9. 10.() () () () () 七、读一读，选一选。
(10分)()1. make dumplings A. 祝你好运()2. good luck B. 对不起，打扰一下()3. get up C. 上山()4. come in D. 跳高()5. by plane E. 起床()6. every day F. 在车站()7. at the station G. 乘飞机()8. do the high jump H. 做饺子()9. up the hill I. 每一天()10. excuse me J. 进来八、根据句意及首字母和汉语提示写单词，补全句子。
(10分)l. I'm h________(饥饿的). I want some noodles.2. We're going to v________(参观) Shanghai tomorrow.3. Look! They're r________(划) a boat.4. I'm riding a h________(马)now.5. Chinese f________(快) food is very nice.6. Do you w________(想要) a Chinese book?7. They are playing c________(国际象棋).8. Lingling is r________(读)a book.9. My father is very s________(健壮的).10. My sister can d________(画) pictures.九、选词填空。
(10分)1. The bus is________(about，at) the station.2. I am________(listen，listening) to music.3. He's reading a book________(about，to) China.4. Mike is________(on，from)the UK.5. There________(is，are)three chickens behind the tree.6. Please________(look，looks) at your book.7. He's playing________(to，with) his dog.8. Let's________(get up，get on) the bus.9. They're rowing a boat________(at，on) the lake.10. I have________(a，an) interesting book.十、用所给词的适当形式填空。
(10分)1. Look！Here________(be)a dog.2. We like________(run).3. She________ (like)swimming.4. He is________(take)pictures.5. What are you________(do)?6. Do you like ________(listen) to music?7. We can see lots of________(interest) things.8. Do you________(want) some rice?9. Here are some________(tomato).10. I'm going to________(winner).词汇专项复习卷一、1. juice 2. light 3. face 4. flower 5. the Spring Festival6. sing7. ride a bike8. present9. clock10. go straight on二、1. A 2. B 3. B 4. A 5. A 6. A7. A8. B9. B10. B三、1. C 2. C 3. C 4. B 5. C 6. A7. C8. C9. C10. C四、1. bread, tomato, potato, dumpling, sweets2. take pictures, fly a kite, row a boat3. bear, chicken, pig, horse4. supermarket, cinema, school, zoo5. plane, bus, train, bike(书写合理正确即可，以上答案供参考)五、1. make 2. boat 3. luck 4. light 5. give 6. fish7. park8. some9. bear10. dinner11. book12. bike13. rice14. tall六、1. B 2. A 3. I 4. J 5. F 6. C7. E8. H9. G10. D七、1. H 2. A 3. E 4. J 5. G 6. I7. F8. D9. C10. B八、1. hungry 2. visit3. rowing点拨：用row的-ing形式。
4. horse5. fast6. want7. chess8. reading点拨：注意使用-ing形式。
9. strong10. draw点拨：can后面跟动词原形。
九、1. at点拨：在车站，用介词at。
2. listening点拨：现在进行时，使用动词的-ing形式。
3. about点拨：关于中国，用介词about。
4. from点拨：来自哪个国家，用介词from。
5. are点拨：three chickens 是复数，所以用are。
6. look7. with8. get on9. on10. an点拨：元音音素前使用冠词an, 常见的还有an elephant / apple/ egg/orange/ice cream/English teacher。
十、1. is点拨：a dog是单数，所以用is。
2. running点拨：like后面跟动词-ing形式。
3. likes点拨：she是第三人称单数，后面的动词要用单三形式likes。
4. taking5. doing6. listening7. interesting点拨：“有趣的事情”，要用interest的形容词interesting。
8. want点拨：助动词do后面跟动词原形。
9. tomatoes点拨：tomato的复数＋es。
10. win点拨：be going to＋动词原形。
期末词汇专题复习(试题)外研版(三起)英语四年级上册
21．My brother is(drink) milk.
22．—Can you ride a bike?
—No, I(can).
23．Sam is(read) a book.
24．—What(be) your mother doing?
【详解】句意：—鱼正在做什么？—它正在河里游泳。分析问句和答语的句子结构，可知句子是现在进行时，现在进行时结构be+动词的现在分词，故答案为doing，swimming。
【点睛】
2．like likes
【详解】略
3．kids
【详解】句意为：看看树下的孩子们。他们在做什么？后一句中用了they，是复数，指代kids。故答案为kids。
___________________________________________________________________________
⑵Do more exercises.(改为否定祈使句)
___________________________________________________________________________
(3)That man has a tomato.（变成复数句子）
Those ________have some ________ .
(4)Noodles with tomato and egg is also very niห้องสมุดไป่ตู้e.（变同义句）
________
参考答案：
1．doing swimming
三、选词/短语填空
选择合适的单词补全句子。
51．—(What/Where)are you doing now?
外研版(一起)英语四年级上册(全) 词句练习 (另有答案)
外研版(一起)英语四年级上册(全) 词句练习Module 1一、写英文单词1.亲爱的____________________________2.健康的____________________________3.的_________________________________4.不久，很快______________________5.告诉，讲述______________________6.爱你的___________________________二、写英文短语1.在星期六_____________________________2.读一封信_____________________________3.在伦敦_______________________________4.身体，状态等）很好_________________5.有一点_______________________________6.一张……的照片_______________________7.生日宴会_____________________________ 8.穿着红色的衣服_________________9.有_______________________________10.写信给我________________________11.告诉我关于……__________________12.长城_____________________________13.电脑游戏_______________________三、翻译句子1. 星期六是我的生日。
_________________________________________________________________________________________ 2. 这是一张我生日宴会的照片。
_________________________________________________________________________________________3. 她有一头又长又黑的头发。
外研版四年级英语上册期末Module1描述位置关系专项试卷附答案.docx
外研版四年级英语上册Module 1描述位置关系一、重点词汇。
（英汉互译）（一）方位词1.左边；向左；左边的 _______________________________________________2.右边；向右；右边的_______________________________________________3.straight __________________________________________________________________4.向右转___________________________________________________________5.向左转___________________________________________________________6.go straight on _____________________________________________________________（二）方位介词1.在 .. 旁边，在... 附近____________________________________________2.接近，临近_______________________________________________________3.紧靠......旁边，贴近_____________________________________________4.behind the tree ____________________________________________________________5.on your right _____________________________________________________________6.at the station _____________________________________________________________7.up the hill________________________________________________________________8.down the hill _____________________________________________________________（三）地点名词1.大街，街道 _______________________________________________________2.超市_____________________________________________________________3.电影院4.房屋_____________________________________________________5.station6. hill _____________________________________________________________（四）其他1. __________________________ 居住2.火车3.excuse me _______________________________________________________________二、重点句子。
外研版(三起)四年级英语上册期末冲刺复习——句子、连词成句专项突破卷【含答案】
外研版（三起）四年级英语上册期末冲刺复习——句子、连词成句专项突破卷班级：_____________姓名：____________ 得分：____________时间：40分钟满分：100分一、连词成句。
(10分)1. am, talking, friend, to, my, I (. )___________________________________________________________________2. going, by, is, to, Shanghai, she, plane (.)___________________________________________________________________3. have, some, can, I, fruit (? )___________________________________________________________________4. is, a, sheep, there, in, photo, this (. )___________________________________________________________________5.to, what, you, on, going, do, sports, are, day (? )___________________________________________________________________二、连词成句。
(10分)1. much the How pen is (? )2. with playing He's Daming football (. )3. draw Can dragon you a (? )4. hill He's the up (. )5. is Tom going to some drink soya milk(. )三、连词成句。
2020年外研版小学英语(三起点)四年级上册期末专项复习试题及答案(全套)
外研版小学英语（三起点）四年级上册词汇专项复习卷60 分钟满分：100 分：时间题号一二三四五六七八九十总分得分(10 分)单词。
一、根据图片补全1. 2. 3. 4.j____ice l____ ____ht f____c f____ow5. 6. 7.the S__r__ __g F__ __ti____ ____l s____ ____ ____ r____d____ab________e8. 9. 10.p____e____e________ c____o____k go s____ ____a____ght on。
(5 分)号内的括二、给单词选出相应的汉语意思并把序号写在题前( )1. cinema A. 电影院B. 房屋( )2. want A. 划船 B. 想要( )3. bread A. 灯 B. 面包( )4. read A.阅读 B. 书写( )5. tomorrow A. 明天 B. 今天( )6. horse A.马B. 羊( )7. kid A. 小孩 B. 饼干( )8. month A. 年 B. 月( )9. run A. 跳 B. 跑( )10. family A. 火车B. 家庭三、选出不同类的单词。
(5 分)( )1. A. month B. day C. metre( )2. A. Halloween B. Christmas C. family( )3. A. jumping B. running C. help( )4. A. tea B. drink C. milk( )5. A. bus B. train C. afraid( )6. A. people B. left C. right( )7. A. beside B. next to C. supermarket( )8. A. horse B. elephant C. face( )9. A. three B. twelve C. station( )10. A. school B. cinema C. clock四、按照要求写一写。
外研版英语小学四年级上学期复习试题与参考答案
外研版英语小学四年级上学期复习试题与参考答案一、听力部分（本大题有12小题，每小题2分，共24分）1、Question: Listen to the recording and choose the picture that matches the sentence you hear.Recording: (A picture of a girl holding a book in a library is shown.) “She is reading a book in the library.”Answer: (Select the picture of the girl reading in the library.)Explanation: The recording describes a girl who is reading a book in the library. The task is to match this description with the corresponding picture.2、Question: Listen carefully and circle the word you hear in the sentence.Recording: “I like to eat an apple for breakfast every day.”Options:•banana•apple•orangeAnswer: appleExplanation: The recording states, “I like to eat an apple for breakfast eve ry day.” The word that matches the sentence is “apple,” which should be circled as the correct answer.3、 Listen to the short conversation and choose the correct answer.A)The book is on the desk.B)The book is in the bag.C)The book is under the chair.Answer: A) The book is on the desk.Explanation: In the listening material, the speaker clearly states that the book is placed on the desk. The answer options refer to different locations of the book, and A is the only one that matches the description given in the audio.4、 Listen to the instructions and answer the question.Question: What is the second task in the list?A)Clean the room.B)Do your homework.C)Set the table for dinner.Answer: B) Do your homework.Explanation: In the listening section, a series of tasks are mentioned, and the speaker asks specifically about the second task. After listing the tasks, if the second task mentioned is “Do your homework,” then B is the correct answer. This question requires attention to detail and memory recall of the sequence of tasks provided in the audio.5、Listen to the dialogue and choose the correct answer.(听对话，选择正确答案)Question: What is the boy going to do tomorrow?A. He’s going to play football.B. He’s going to visit his grandparents.C. He’s going to have a picnic.Answer: BExplanation: The dialogue mentions that the boy tells his mother he is not going to play football tomorrow because he is going to visit his grandparents. This directly corresponds to option B, “He’s going to visit his grandparents.”6、Listen to the passage and answer the question.(听短文，回答问题)Question: How many days are there in a week?A. Five days.B. Six days.C. Seven days.Answer: CExplanation: The passage should mention that there are seven days in a week, which includes Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday. This corresponds to option C, “Seven days.”7、Listen to the dialogue and choose the correct answer.Question: What does the boy want to be when he grows up?A. A teacher.B. A doctor.C. A scientist.Answer: BExplanation: The dialogue may contain a sentence like, “I want to help people when they are sick. So, I want to be a doctor when I grow up.” Thisresponse indicates that the boy wants to be a doctor, hence the answer is B.8、Listen to the passage and answer the question.Question: How many books does the library have in total?A. 2,000 books.B. 3,500 books.C. 5,000 books.Passage Preview: (Note: This is a preview to help construct the answer and explanation, as the actual passage will be spoken.) “Our s chool library is a treasure trove of knowledge. It houses over 3,000 books on various subjects, ranging from fiction to science. Last year, we added another 500 books to our collection, bringing the total number of books to…”Answer: BExplanation: Based on the passage preview, it mentions that the library originally had over 3,000 books and last year added another 500 books. Adding these two numbers together (3,000 + 500 = 3,500), we can determine that the library now has 3,500 books in total, hence the answer is B.9、Listen to the passage and choose the correct answer to the question. Question: What’s the boy’s favorite sport?A. Football.B. Basketball.C. Swimming.Answer: A. Football.Explanation: The passage mentions that the boy likes playing football very much, so his favorite sport is football.10、Listen to the dialogue and fill in the blank with the missing word. Dialogue:Girl: Hi, Tom! What are you doing?Boy: Hi, Lily! I’m_______my model plane.Girl: It looks great! Can I have a look?Boy: Sure, here you are.Answer: makingExplanation: The dialogue suggests that the boy is in the process of creating something, and given the context of “my model plane,” the missing word is most likely “making.”11、Listen to the recording and choose the correct answer.Question: What time does the class start in the morning?A)8:00 amB)8:30 amC)9:00 amAnswer: B) 8:30 amExplanation: The recording would have stated the exact time when the class starts in the morning, and based on the common school timings, option B, “8:30 am,” is a likely answer.12、Listen to the conversation and answer the question.Question: Who is going to the library after school?A)SarahB)TomC)Both Sarah and TomRecording: “Sarah, are you going to the library after school today?” “Yes, I am. Are you coming too, Tom?” “Sure, I’ll join you.”Answer: C) Both Sarah and TomExplanation: The conversation indicates that both Sarah and Tom are planning to go to the library after school. Sarah asks Tom if he’s coming, and Tom confirms that he will join her.二、选择题（本大题有12小题，每小题2分，共24分）1.Which word does NOT belong in the group?A. CatB. DogC. TreeD. FishAnswer: CExplanation: This question tests the ability to identify the odd one out in a group of related words. Among the options, “Cat,” “Dog,” and “Fish” are all animals, while “Tree” is a plant. Therefore, “Tree” does not belong in the group of animals.2.Which sentence is grammatically correct?A. I have went to the park yesterday.B. Yesterday, I went to the park.C. I went to the park, yesterday.D. The park, I went yesterday.Answer: BExplanation: This question tests knowledge of English grammar, specifically tense usage and sentence structure. Option A is incorrect because “have” and “went” are not correctly paired; “have gone” is present perfect tense, while “went” is past simple tens e. Option C is grammatically correct but is less preferred in formal writing due to the comma placement, which slightly disrupts the flow. Option D has an incorrect sentence structure, with the subject and verb misplaced. Option B is both grammatically correct and follows a natural sentence structure.3、Which of the following is not a type of weather?A. SunnyB. RainyC. TallAnswer: CExplanation: “Sunny” and “Rainy” are both descriptions of weather conditions, while “Tall” describes a physical attribute (usually of height) and not a weather condition.4、What is the correct plural form of the word “child”?A. ChildsB. ChildrensC. ChildrenAnswer: CExplanation: The plural form of “child” is “children”. “Childs” and “Childrens” are incorrect formations. “Childrens” is particularly incorrect because it tries to make “children” possessive, but “children” itself is already the plural form and does not need a possessive ending.5、Which word can’t fit in the sentence “The sky is_______today.”?A. blueB. yellowC. clearD. sunnyAnswer: BExplanation: In the sentence “The sky is_______today,” the most appropriate adjectives would describe the color or condition of the sky. “Blue” (A) is a common color for the sky, especially on clear days. “Clear” (C) means the sky is free from clouds or obstructions. “Sunny” (D) also describes a sky that is bright and clear because of the sun shining. However, “yellow” (B) is nota typical color for the sky, and it wouldn’t fit well in this context.6、Choose the correct verb form to complete the sentence:“She usually_____her homework at 7:00 pm.”A. doB. doesC. doingD. didAnswer: BExplanation: The sentence “She usually_____her homework at 7:00 pm” requires a verb form that agrees with the subject “She” and expresses a habit ual action in the present tense. The subject “She” is singular, so we need a singular verb form. Option A, “do,” is the base form of the verb and is used for plural subjects or in the first and second person singular. Option B, “does,” is the third-person singular present tense form of “do,” which matches the subject “She” and the time expression “usually.” Option C, “doing,” is the present participle form and is not suitable for this sentence. Option D, “did,” is the past tense form and doesn’t match the present tense context of “usually.” Therefore, the correct answer is B.7、What is the main idea of the passage?A. The history of computers.B. The importance of technology.C. The advantages of online shopping.D. The development of the Internet.Answer: CExplanation: The passage discusses the convenience and advantages of onlineshopping, such as saving time, having a wider range of choices, and being able to compare prices easily. Therefore, the main idea is the advantages of online shopping, making option C the correct answer.8、Which of the following is NOT a reason why people enjoy traveling?A. To relax and unwind.B. To learn about new cultures.C. To escape from daily responsibilities.D. To increase the risk of accidents.Answer: DExplanation: Traveling is generally seen as an enjoyable and enriching activity, allowing people to relax, unwind, and learn about new cultures. While traveling does involve some risk, increasing the risk of accidents is not a reason why people enjoy traveling. Therefore, option D is not a reason and is the correct answer.9、I often play football_______my friends after school.A. withB. andC. to答案：A解析：本题考查的是介词的用法。
外研版(三起)四年级英语(上册)第一次月考总复习及答案
外研版（三起）四年级英语(上册)第一次月考总复习及答案题序一二三四五六七八总分得分（满分：100分时间：60分钟）一、从下列每组单词中选出不同类的一项。
（10分）1、（）A．happen B．hospital C．town2．（）A．face B．nose C．water3．（）A．thirsty B．fever C．hungry4．（）A．headache B．chocolate C．stomachache 5．（）A．fall B．carry C．found二、选出下列各组单词中画线部分的读音不同的一项。
（10分）1．（）A．note B．mom C．dog2．（）A．face B．dad C．name3．（）A．like B．rice C．big4．（）A．me B．she C．red5．（）A．cut B．up C．use三、给下列图片选择对应的单词。
（10分）A．vegetables B．chicken C．noodles D．beef E. soup 1．( )2．( )3．( ) 4．( )5．( )四、单项选择。
（20分）1、—I have a toy pig here. Do you like _____?( )—Yes, I _____.A．it; do B．that; like C．me; don’t 2、—Do you have a library? ( )—______. We have one. It’s on the second floor.A．Yes B．No C．OK 3、—_______ red skirt is this? ( )—It’s Jenny’s skirt.A．Whose B．Where C．What4、They are blind. They _______ see. ( )A．can B．cannot C．are5、________ your name?( )A．What B．What's C．Whats’6、—Do you have _____ pears?( )—No, I have _____ bananas.A．some; any B．any; some C．any; any 7、—______ is it? ( )—It’s 6:30 p.m. It’s time to have dinner.A．What time B．What’s time C．How many 8、_____ flying a kite in the park.( )A．His B．He C．He’s9、The ________ have long necks.( )A．elephants B．giraffes C．turkeys 10、They have two ________ pencils.( ) A．hundreds B．hundreds of C．hundred五、情景交际，选出正确的一项。
外研版(三起)英语四年级上册全册同步练习(20套)附答案
Module 1 Unit 1 Go straight on.一、选出与所给单词是同类的一项。
() 1. right A. B. C. () 2. you A. B. C. () 3. up A. B. C. () 4. dog A. B. C.() 5. cinema A. B. C.二、红花配绿叶。
A. B. C. D. E.1. 2. 3.()()()4. 5.()()三、根据图片选择对应的短语。
() 1. A. turn left B. turn right() 2. A. go straight on B. behind the door() 3. A. next to a supermarket B. on your right() 4. A. in the tree B. behind the tree() 5. A. on your left B. beside the cinema 四、给下列句子或对话选择合适的图片。
() 1. Turn left. You can see the zoo. A.() 2. Where is the cinema? B.() 3. The cat is lost. C.() 4. It's next to a park. D.()5.—Where are you?—We're behind the door. E.五、情景交际。
()1.当你想要问路时，你应该先说：________A. Excuse me.B. Sorry.()2.当体育老师发出指令“Turn left. ”时，你应该：________A.向右转。
B.向左转。
()3.你想要去超市，但是不知道路，你应该问：________A. Where's the supermarket?B. Is it a supermarket?()4.当你想要表达感谢时，你应该说：________A. Thank you so much.B. You're welcome.()5.当别人问你的家庭住址时，你应该说：________A. I'm on your left.B. I live at No. 2 Park Street.答案：一、1. B 2. B 3. C 4. C 5. A二、1. C 2. A 3. B 4. E 5. D三、1. B 2. A 3. A4. B点拨：behind the tree 意为“在树后”。
2024年外研版四年级上册英语单词拼写专项习题
2024年外研版四年级上册英语单词拼写专项习题班级：_____________ 姓名：_____________【单词拼写】1. 根据汉语提示，写出单词。
1. This is a red ________ (毛衣).2. ________(这些) are trouser.3. (小姐)________ Liu is my teacher.4. -- What ________(天) is it today?-- It’s ________ (周一)2. 根据图片提示，补全单词或短语。
［1］playgr__ __nd ［2］lib__ __ry［3］c__ __puter ［4］__ __t room ［5］t__ __chers'' offi__ __ ［6］m__ __ic room ［7］f__ __st floor ［8］se__ __nd floor3. 按要求写单词。
1. write(名词)_______________2.run(现在分词) _______________3.meet(过去式)_______________4.took(原形) _______________5.first(基数词)_______________6. happy(反义词)_______________7.baby(复数)_______________8.skip(ing形式) _______________9.good（副词）_______________ 10.he(宾格)_______________4. 根据图意和首字母提示，写出单词，完成句子。
［1］Miss Liu is busy in her o_______.［2］I have a brother. He has a pair of brown s_______.［3］Tom is a f_______. He is cool.［4］Look, the rabbit can run and j_______.［5］Mum needs three p_______ and two eggs.5. 按要求写单词。
新版四年级上册英语试题-分类专项复习卷：语音与词汇 外研版 含答案
教科版（广州）英语四年级上册分类专项复习卷：语音与词汇一、选择题1.A. game B. jacket C. map2.A. eat B. he C. bed3.A. nice B. writer C. window4.A. like B. small C. school5.A. music B. study C. use选出每组单词中不同类的选项。
6.A. study B. bedroom C. story7.A. window B. open C. close8.A. between B. pupil C. nurse9.A. socks B. garden C. sweater10.A. twelve B. classroom C. thirty 根据短语选择相应的图片。
11.dining hall （）A. B.12.do homework （）A. B.13.sing songs （）A. B.14.have meals （）A. B.15.at room （）A. B.16.bathroom （）A. B.二、判断题17.English she ________18.chair school ________19.flower grow ________20.what who ________21.this thirty ________看图，判断下列短语与图意是（T）否（F）相符。
22.under the table _______23.read books _______24.a pair of shorts _______25.behind the box _______26.grow flowers _______27.understand the world _______28.swimming pool _______29.between two doors _______30.help sick people _______三、音标题A. mayB. highC. pleaseD. nightE. mouseF. aboutG. sayH. countI. meetJ. play31.stay ________32.clean ________33.right ________34.house ________判断下列每组单词画线部分有几种读音，按A、B、C三种情况选择。