Unit 4 单项选择（连词and, but和because）-2024-2025学年七年级英语上册单元语法分题型全面突破（人教版2024）

Unit 4 My Favourite Subject 语法专项 连词and, but和because 单项选择连词and, but和because 1．Practice more, ________ you will learn English well. A．or B．and C．but D．because 2．Mary thinks geography is really difficult, ________ she doesn’t like it. A．but B．because C．so D．and 3．—Do you watch sports every day? —No, I don’t. ________ I play pingpong ________ tennis every day. So I can play them well. A．But; of B．And; but C．But; and 4．The countryside is so nice ________ quiet. A．so B．or C．and D．but 5．Mike ________ Tim are in the restaurant, ________ Milly is not. A．and; and B．but; but C．and; but D．but; and 6．—I think math is difficult ________ boring. I don’t like it. —________ Jill likes it very much. She says it’s interesting. A．but; And B．but; But C．and; And D．and; But 7．I like English ________ Chinese. I think they’re difficult ________ interesting. A．and; and B．and; but C．but; and D．but; but 8．Bob ________ Bill are in the same school, ________ they aren’t in the same class. A．and; and B．and; but C．but; but 9．—Does Gu Ailing speak Chinese? —Yes, she does. ________ she won (赢) 3 medals (奖牌) for China. A．And B．But C．So 10．My favorite subject is Chinese, ________ Mary’s favorite subject is English. A．and B．but C．because D．so 11．My People, My Country is a good movie _______ we love it very much. A．but B．and C．or D．though (虽然) 12．—Are the watch ______ the radio his? —The watch is his, ______ the radio isn’t his. A．and; and B．and; but C．but; and 13．I have a brother ________ two sisters, ________ Jack doesn’t. A．and; but B．but; and C．and; and 14．—I have a volleyball ______ two ping-pong balls. —Well, I have two volleyballs, ______ I don’t have a ping-pong ball. A．and; and B．but; but C．but; and D．and; but 15．He is riding a bike, ______ it starts to rain. A．and B．but C．with 16．—How was your holiday? —It was a bad day ______ also a good day. A．so B．but C．/ 17．This dress looks nice ________ it’s too small for me. A．till B．but C．because 18．Tony can speak French well now, ________ he couldn’t speak it at all last year. A．and B．but C．or D．so 19．I’m not good at English speaking ________ I won’t give up. A．and B．but C．or D．because 20． Giraffes can run fast ________ they cannot run for a long time. A．and B．but C．or D．so 21．—Well done, Lisa! You are the first in the math contest. —Thanks. In my eyes, math is difficult ________ interesting and magic. A．but B．and C．so D．or 22．Ms. Chen has a bad cold, _______ she still keeps on working as usual. A．because B．so C．or D．but 23．The little boy is only 5 years old, _________ he can make cakes (做蛋糕). A．and B．so C．or D．but 24．I looked everywhere ________ I still couldn’t find my pen. I had to ask mom for help. A．so B．because C．when D．but 25．I got up late this morning, ________ I didn’t catch the early bus. A．because B．so C．but 26．Pandas are very lovely, _______ many people love them. A．because B．so C．or D．but 27．She likes to wear red coats ________ she thinks it’s a symbol of good luck. A．so B．or C．because D．but 28．________ I’m late again, ________ the teacher is very angry. A．Because, so B．So, / C．Because, / 29．It’s easy for students to buy things ________ there are many stores near the school. A．but B．or C．because D．so 30．Tim likes to help others, ________ we all enjoy being with him. A．because B．but C．or D．so 31．—Why do you like this book? —________ it’s great fun. A．Because B．So C．And D．But 32．The book is too boring, ________ I don’t like it. A．and B．so C．because D．but 33．Mike is English, ________ he speaks English very well. A．and B．but C．or D．so 34．The pandas are cute, ________ I like them a lot. A．so B．or C．but D．if 35．I don’t like apples, ________ I don’t want to eat apples. A．so B．but C．and 36．My brother always plays sports, ________ he is very healthy. A．but B．or C．so D．because 37．—I don’t like to read in the sun _________ it is bad for my eyes. —You are right. A．but B．and C．so D．because 38．My father ________ my mother are both teachers, ________ my uncle isn’t. He is an engineer(工程师)． A．and; but B．and; and C．but; but 39．I like basketball _______ baseball, _______ I can’t play them. A．and; and B．but; but C．and; but D．but; and 40．—I want to be a teacher when I grow up. —Work hard, ________ your dream will come true. A．or B．but C．though D．and 41．My name is Zhang Ping ________ I’m from China. A．and B．so C．but 42．Betty speaks English best in our class she often helps us with it. A．and B．but C．or D．for 43．I have a brother ________  two sisters,  ________  Jack doesn’t. A．and, and B．but, and C．and, but D．but, but 44．I'm Kate, ________ my sister is Gina. I'm tidy, ________ Gina isn't. A．but; and B．and; but C．and; and D．but; but 45．My name is Zhang Ping ________ I'm from China. A．and B．so C．but 46．To have a bright future, we should 　　　　 study hard 　　　　 keep in good health. A．not; but B．not only; but also C．neither; nor D．either; or 47．I don’t like ice-cream, ______ my sister does. A．so B．and C．but 48．He lost his dictionary in the school library, ______ he found it in the Lost and Found Box in the classroom! A．and B．but C．or D．so 49．Mary likes ice-cream, ________ I don’t like it. A．and B．or C．but 50．I like tomatoes ________ I don’t like pears. A．and B．but C．so D．because 原创精品资源学科网独家享有版权，侵权必究！1 学科网（北京）股份有限公司 $$ Unit 4 My Favourite Subject 语法专项 连词and, but和because 单项选择连词and, but和because 1．Practice more, ________ you will learn English well. A．or B．and C．but D．because 【答案】B 【详解】句意：多练习，你就会学好英语。 考查连词的用法。or或者；and和；but但是；because因为。根据“Practice more…you will learn English well”可知，这是祈使句+and/or+陈述句的一个结构，前后是递进关系，应填and，故选B。 2．Mary thinks geography is really difficult, ________ she doesn’t like it. A．but B．because C．so D．and 【答案】C 【详解】句意：玛丽认为地理太难了，因此她不喜欢地理。 考查连词用法。but但是，表转折；because因为，表原因；so因此，表因果；and和，表并列。分析前后两句关系可知，此处表结果。故选C。 3．—Do you watch sports every day? —No, I don’t. ________ I play pingpong ________ tennis every day. So I can play them well. A．But; of B．And; but C．But; and 【答案】C 【详解】 句意：——你每天看体育比赛吗？ ——不，我不看。但我每天都打乒乓球和网球。所以我可以打得很好。 考查并列连词辨析。but但是；and和，然后，并且；of……的。第一个空，根据“—Do you watch sports every day? —No, I don’t...I play pingpong ...tennis every day.”可知前后表示转折，用But。第二个空，根据“I play pingpong...tennis every day. So I can play them well.”可知这里连接并列名词pingpong和tennis，用and。故选C。 4．The countryside is so nice ________ quiet. A．so B．or C．and D．but 【答案】C 【详解】句意：乡村是如此的美丽和宁静。 考查连词词义辨析。so因此；or或者；and和；but但是。根据空前的“nice”和空后的“quiet”的词义可知，此处表示并列关系。故选C。 5．Mike ________ Tim are in the restaurant, ________ Milly is not. A．and; and B．but; but C．and; but D．but; and 【答案】C 【详解】句意：迈克和蒂姆在餐厅，但米莉不在。 考查连词的用法。and和；but但是。根据“Mike...Tim are in the restaurant”可知第一空连接并列名词Mike和Tim，应用and；第二个空，由“Milly is not.”可知，表示转折，用but。故选C。 6．—I think math is difficult ________ boring. I don’t like it. —________ Jill likes it very much. She says it’s interesting. A．but; And B．but; But C．and; And D．and; But 【答案】D 【详解】句意：——我认为数学又难又无聊。我不喜欢它。——但是吉尔很喜欢它。她说它很有趣。 考查连词辨析。but但是，表转折；and和，表并列。第一个空，difficult和boring是并列关系，所以用and；第二个空，前面“我”不喜欢，和后面的吉尔喜欢，为转折关系，所以用but，此处为句子开头，首字母大写。故选D。 7．I like English ________ Chinese. I think they’re difficult ________ interesting. A．and; and B．and; but C．but; and D．but; but 【答案】B 【详解】句意：我喜欢英语和语文。我觉得它们很难但很有趣。 考查连词词义辨析。and和；but但是。根据“I like English…Chinese.”以及“I think they’re”可知，我喜欢英语和语文，因此要说学科的优点，所以第一空用“and”表示并列关系。并且这两个学科应该是“难但很有趣”，所以第二空用“but”表示转折关系。故选B。 8．Bob ________ Bill are in the same school, ________ they aren’t in the same class. A．and; and B．and; but C．but; but 【答案】B 【详解】句意：鲍勃和比尔在同一所学校，但他们不在一个班级。 考查连词辨析。and和；but但是。根据“are”可知，主语是复数，因此第一空用and连接两个并列名词；根据“they aren’t in the same class”可知，前后两句是转折关系，因此第二空but符合句意。故选B。 9．—Does Gu Ailing speak Chinese? —Yes, she does. ________ she won (赢) 3 medals (奖牌) for China. A．And B．But C．So 【答案】A 【详解】句意：——谷爱凌说中文吗？——是的，她说。并且她为中国赢得了三枚奖牌。 考查连词辨析。And和；But但是；So因此。“Yes,she does.”与“she won (赢) 3 medals (奖牌) for China.”是并列关系，用and连接，故选A。 10．My favorite subject is Chinese, ________ Mary’s favorite subject is English. A．and B．but C．because D．so 【答案】A 【详解】句意：我最喜欢的科目是语文，玛丽最喜欢的科目是英语。 考查连词辨析。and和；but但是；because因为；so所以。分析两个句子可知，前后两句是并列关系，用and连接。故选A。 11．My People, My Country is a good movie _______ we love it very much. A．but B．and C．or D．though (虽然) 【答案】B 【详解】句意：《我和我的祖国》是一部好电影，我们非常喜欢它。 考查连词辨析。but但是，表转折关系；and和，表顺接关系；or或者，表选择关系；though虽然，从属连词，引导让步状语从句。结合句意可知，前后半句表示顺接关系，所以用连词and连接。故选B。 12．—Are the watch ______ the radio his? —The watch is his, ______ the radio isn’t his. A．and; and B．and; but C．but; and 【答案】B 【详解】句意：——手表和收音机是他的吗？——手表是他的，但是收音机不是他的。 考查连词。and和；but但是。第一个空，连接并列名词watch和radio，用and连接；第二个空，前面是肯定形式，后面是否定形式，用but连接表示转折。故选B。 13．I have a brother ________ two sisters, ________ Jack doesn’t. A．and; but B．but; and C．and; and 【答案】A 【详解】句意：我有一个哥哥和两个姐姐，但杰克没有。 考查连词辨析。and和；but但是。第一个句子中a brother和two sisters是并列关系，用and连接；第二个句子的句意与前文是转折关系，所以第二个空填but。故选A。 14．—I have a volleyball ______ two ping-pong balls. —Well, I have two volleyballs, ______ I don’t have a ping-pong ball. A．and; and B．but; but C．but; and D．and; but 【答案】D 【详解】句意：——我有一个排球和两个乒乓球。——我有两个排球，但是我没有乒乓球。 考查并列连词辨析。and和，并列连词，表并列关系；but但是，并列连词，表转折关系。根据语境可知，第一个空表示并列，所以用 and，意为“和”；第二个空表示转折，所以用but，意为“但是”。故选D。 15．He is riding a bike, ______ it starts to rain. A．and B．but C．with 【答案】B 【详解】句意：他正在骑自行车，但是开始下雨了。 考查词汇辨析。and和；but但是；with和……一起。分析题干可知，前后两个句子是转折关系，连词but符合语境。故选B。 16．—How was your holiday? —It was a bad day ______ also a good day. A．so B．but C．/ 【答案】B 【详解】句意：——你的假期过得怎么样？——是糟糕的一天但也是美好的一天。 考查连词辨析。so所以；but但是；/不填。分析句子，前后表示转折关系，用but连接，故选B。 17．This dress looks nice ________ it’s too small for me. A．till B．but C．because 【答案】B 【详解】句意：这件衣服看起来不错，但是对我来说太小了。 考查连词辨析。till直到；but但是；because因为。根据“looks nice”和“it’s too small for me”可知，前后之间是转折关系，所以用but连接，故选B。 18．Tony can speak French well now, ________ he couldn’t speak it at all last year. A．and B．but C．or D．so 【答案】B 【详解】句意：托尼现在法语说得很好，但去年他一点也不会说。 考查连词辨析。and和；but但是；or或者；so因此。根据“Tony can speak French well now…he couldn’t speak it at all last year.”可知，前后句之间为转折关系，应用but表示转折，意为“但是”。故选B。 19．I’m not good at English speaking ________ I won’t give up. A．and B．but C．or D．because 【答案】B 【详解】句意：我不擅长英语口语，但我不会放弃。 考查连词辨析。and和；but但是；or或者；because因为。根据“I’m not good at English speaking”以及“I won’t give up”可知，前后句之间表达的是转折关系，应该用but连接。故选B。 20． Giraffes can run fast ________ they cannot run for a long time. A．and B．but C．or D．so 【答案】B 【详解】句意：长颈鹿可以跑得很快，但它们不能跑很长时间。 考查连词辨析。and和，然后；but但是；or或者，否则；so因此。根据上文“Giraffes can run fast长颈鹿可以跑得很快”与“they cannot run for a long time不能跑很长时间”之间为转折关系，应用连词but表示转折，意为“但是”。故选B。 21．—Well done, Lisa! You are the first in the math contest. —Thanks. In my eyes, math is difficult ________ interesting and magic. A．but B．and C．so D．or 【答案】A 【详解】句意：——干得好，丽莎！你在数学竞赛中得了第一名。——谢谢。在我看来，数学很难，但很有趣，并且神奇。 考查连词辨析。but但是，表示转折；and和，又，表示顺承；so所以，表示因果；or或者，否则，表示选择。前句“math is difficult”和此句“interesting and magic”构成转折关系，故选A。 22．Ms. Chen has a bad cold, _______ she still keeps on working as usual. A．because B．so C．or D．but 【答案】D 【详解】句意：陈女士感冒严重，但是她仍然像往常一样继续工作。 考查连词辨析。because因为（表因果关系）；so所以（表因果关系）；or或者（表选择关系）；but但是（表转折关系）。由“Ms Chen has a bad cold,…she still keeps on working as usual”可知，陈女士感冒严重，但是她仍然像往常一样继续工作，句子前后是转折关系，应用but。故选D。 23．The little boy is only 5 years old, _________ he can make cakes (做蛋糕). A．and B．so C．or D．but 【答案】D 【详解】句意：这个小男孩只有5岁，但他会做蛋糕。 考查连词辨析。and和；so因此；or或者；but但是。根据“The little boy is only 5 years old”以及“he can make cakes (做蛋糕).”可知，设空处前后存在转折关系，but符合语境。故选D。 24．I looked everywhere ________ I still couldn’t find my pen. I had to ask mom for help. A．so B．because C．when D．but 【答案】D 【详解】句意：我到处找但是还是找不到我的钢笔。我只好向妈妈求助了。 考查连词辨析。so所以；because因为；when当……的时候；but但是。空格前后两句存在转折关系，用but连接。故选D。 25．I got up late this morning, ________ I didn’t catch the early bus. A．because B．so C．but 【答案】B 【详解】句意：我今天早上起晚了，所以没赶上早班车。 考查连词辨析。because因为；so因此；but但是。“I got up late this morning”与“I didn’t catch the early bus”是因果关系，是“前因后果”，故选B。 26．Pandas are very lovely, _______ many people love them. A．because B．so C．or D．but 【答案】B 【详解】句意：熊猫非常可爱，因此很多人喜欢它们。 考查连词辨析。because因为；so因此；or或者；but但是。“Pandas are very lovely”（熊猫非常可爱）是后半句“many people love them”（很多人喜欢它们）的原因，前因后果，空格处表示“因此，所以”，应用so连接。故选B。 27．She likes to wear red coats ________ she thinks it’s a symbol of good luck. A．so B．or C．because D．but 【答案】C 【详解】句意：她喜欢穿红色的外套，因为她认为这是好运的象征。 考查连词辨析。so因此；or或者；because因为；but但是。根据“She likes to wear red coats ... she thinks it’s a symbol of good luck.”可知，前后句为因果关系，此处表示原因，应用because。故选C。 28．________ I’m late again, ________ the teacher is very angry. A．Because, so B．So, / C．Because, / 【答案】C 【详解】句意：因为我又迟到了，所以老师非常生气。 考查连词辨析。because因为；so所以。because和so不能连用，因此可先排除选项A；首句不能用so，可排除选项B。故选C。 29．It’s easy for students to buy things ________ there are many stores near the school. A．but B．or C．because D．so 【答案】C 【详解】句意：学生们买东西很容易，因为学校附近有很多商店。 考查连词辨析。but但是；or或者；because因为；so所以。根据“It’s easy for students to buy things”及“there are many stores near the school.”可知，前后句为因果关系，后句为解释前句购物方便的原因，应用表示原因的连词because引导原因状语从句，意为“因为”。故选C。 30．Tim likes to help others, ________ we all enjoy being with him. A．because B．but C．or D．so 【答案】D 【详解】句意：Tim喜欢帮助别人，所以我们都喜欢和他在一起。 考查连词辨析。because因为；but但是；or或者；so因此。根据“Tim likes to help others, ... we all enjoy being with him.”可知，前后句为因果关系，此处表示结果，应用so。故选D。 31．—Why do you like this book? —________ it’s great fun. A．Because B．So C．And D．But 【答案】A 【详解】句意：——你为什么喜欢这本书？——因为它很有趣。 考查连词辨析。Because因为；So因此；And和；But但是。根据“Why do you like this book?”可知，此处回答原因，用because。故选A。 32．The book is too boring, ________ I don’t like it. A．and B．so C．because D．but 【答案】B 【详解】句意：这本书太无聊了。所以我不喜欢它。 考查连词辨析。and和；so因此；because因为；but但是。“The book is too boring,”与“I don’t like it”是因果关系，遵循“前因后果”，故选B。 33．Mike is English, ________ he speaks English very well. A．and B．but C．or D．so 【答案】D 【详解】句意：迈克是英国人，所以他英语说得很好。 考查连词辨析。and和；but但是；or或者；so所以。根据“Mike is English...he speaks English very well.”可知，前后句是因果关系，应用so连接，故选D。 34．The pandas are cute, ________ I like them a lot. A．so B．or C．but D．if 【答案】A 【详解】句意：熊猫很可爱，所以我很喜欢它们。 考查连词辨析。so所以；or或者；but但是；if如果。根据“The pandas are cute, ... I like them a lot.”可知，前后句为因果关系，此处表示结果，应用so。故选A。 35．I don’t like apples, ________ I don’t want to eat apples. A．so B．but C．and 【答案】A 【详解】句意：我不喜欢苹果，所以我不想吃苹果。 考查连词辨析。so所以；but但是；and并且。根据“I don’t like apples...I don’t want to eat apples.”可知，前后句是因果关系，应用so表示结果，故选A。 36．My brother always plays sports, ________ he is very healthy. A．but B．or C．so D．because 【答案】C 【详解】句意：我哥哥总是运动，所以他很健康。 考查连词的用法。but但是；or或者、否则；so所以； because因为。根据“My brother always plays sports”和“he is very healthy.”可知空格前后句为因果关系，前因后果，所以此处应用so表“所以”，故选C。 37．—I don’t like to read in the sun _________ it is bad for my eyes. —You are right. A．but B．and C．so D．because 【答案】D 【详解】句意：——我不喜欢在太阳下看书因为这对我的眼睛不好。——你说得对。 考查连词辨析。but但是，表转折关系；and和，表顺承关系；so所以，表因果关系；because因为，表因果关系。根据“I don’t like to read in the sun...it is bad for my eyes”可知，两句是因果关系，且空后句表达原因。故选D。 38．My father ________ my mother are both teachers, ________ my uncle isn’t. He is an engineer(工程师)． A．and; but B．and; and C．but; but 【答案】A 【详解】句意：我爸爸和妈妈都是老师，但我叔叔不是。他是一名工程师。 考查并列连词。and和，表并列关系；but但是，表转折关系。根据句中“are both teachers”可知，第一空表示我爸爸和妈妈，是并列关系，应用and；又根据“He is an engineer.”可知，第二空表转折，应用but，故选A。 39．I like basketball _______ baseball, _______ I can’t play them. A．and; and B．but; but C．and; but D．but; and 【答案】C 【详解】句意：我喜欢篮球和棒球，但是我都不会打。 考查并列连词。根据“I like basketball…baseball”可知，篮球和棒球是都喜欢，是并列的两个名词，因此填and；根据“I can’t play them”可知，本句与前面存在转折关系，因此填but。故选C。 40．—I want to be a teacher when I grow up. —Work hard, ________ your dream will come true. A．or B．but C．though D．and 【答案】D 【详解】句意：——我长大后想要成为一名教师。 ——努力工作，你的梦想将会实现。 考查连词辨析。or或者，否则；but但是；though虽然；and和。根据 “work hard”和 “your dream will come true”可知前后两个句子是顺承关系，用and，此处构成结构：祈使句，and+陈述句。故选D。 41．My name is Zhang Ping ________ I’m from China. A．and B．so C．but 【答案】A 【详解】句意：我叫张平，来自中国。 考查并列连词。and和；so因此；but但是；空格前后两句之间是并列关系，应用and连接，故选A。 42．Betty speaks English best in our class she often helps us with it. A．and B．but C．or D．for 【答案】A 【详解】句意：在我们班贝蒂英语讲得最好，并且她经常帮助我们学英语。 考查并列连词。and和；but但是；or或者；for因为。结合语 境可知，空处表示顺承关系，用and连接前后句，故选A。 43．I have a brother ________  two sisters,  ________  Jack doesn’t. A．and, and B．but, and C．and, but D．but, but 【答案】C 【详解】句意：我有一个哥哥和两个妹妹，但是Jack没有。 考查连词辨析。and和；but但是。第一个句子中brother和sisters是并列关系，用and连接。第二个句子“Jack没有”与前文是转折关系，所以第二个空填but，故选C。 44．I'm Kate, ________ my sister is Gina. I'm tidy, ________ Gina isn't. A．but; and B．and; but C．and; and D．but; but 【答案】B 【详解】句意：我是凯特，我妹妹是吉娜。我很整洁，但吉娜不是。 考查连词辨析。but但是，表示转折关系；and和、并且，表示并列、顺承关系。根据“I'm Kate, … my sister is Gina.”可知前后句之间是并列关系，因此用and连接；再根据“I'm tidy, … Gina isn't.”可知前后句之间是转折关系，因此用but连接；故选B。 45．My name is Zhang Ping ________ I'm from China. A．and B．so C．but 【答案】A 【详解】句意：我叫张平，来自中国。 考查并列连词。and和；so因此；but但是；空格前后两句之间是并列关系，应用and连接，故选A。 46．To have a bright future, we should 　　　　 study hard 　　　　 keep in good health. A．not; but B．not only; but also C．neither; nor D．either; or 【答案】B 【详解】句意：为了有一个光明的未来，我们不仅要努力学习而且要保持健康。 考查并列连词用法。not…but…不是……而是……；not only…but also…不仅……而且……；neither…nor…既不……也不……；either…or…或者……或者……。根据“To have a bright future”可知，这里指为了好的未来既要努力学习，又要保持健康，故选B。 47．I don’t like ice-cream, ______ my sister does. A．so B．and C．but 【答案】C 【详解】句意：我不喜欢冰淇淋，但我妹妹喜欢。 考查连词辨析。so因此；and和；but但是。根据“I don’t like ice-cream…my sister does”可知，设空处前后存在转折关系，填转折连词but。故选C。 48．He lost his dictionary in the school library, ______ he found it in the Lost and Found Box in the classroom! A．and B．but C．or D．so 【答案】B 【详解】句意：他在学校图书馆丢了他的字典，但是他在教室的失物招领处找到了它。 考查连词辨析。and和，表示并列；but但是，表示转折；or或者，表示选择；so因此，表示因果。分析前后句关系可知是转折关系，因此用“but”。故选B。 49．Mary likes ice-cream, ________ I don’t like it. A．and B．or C．but 【答案】C 【详解】句意：玛丽喜欢冰淇淋，但我不喜欢。 考查连词词义辨析。and和，表示并列关系；or 或者，表示选择关系；but但是，表示转折。由likes和don’t like可知，设空前后句意为转折关系。故选C。 50．I like tomatoes ________ I don’t like pears. A．and B．but C．so D．because 【答案】B 【详解】句意：我喜欢西红柿，但是我不喜欢梨。 考查连词辨析。and和；but但是；so所以；because因为。前后两句是转折关系，用but连接。故选B。 原创精品资源学科网独家享有版权，侵权必究！1 学科网（北京）股份有限公司 $$