【学业水平】北京市2019年普通高中第一次合格性学业水平考试英语试题
2019年北京市第一次普通高中学业水平合格性考试英语试卷一、听力理解(共25小题,25分。
每小题1分)第一节:听下面十段对话或独白,从各题A、B、C三个选项中,选出能回答问题的最佳答案。
每段对话或独白你将听两遍。
听第1段材料,回答第1题。
1. What is the man going to do this Saturday?A. Go hiking.B. Visit his grandparents.C. Have a picnic.听第2段材料,回答第2题。
2. Where was the man born?A. In England.B. In New Zealand.C. In Russia.听第3段材料,回答第3题。
3. When will the speakers leave for the airport?A. At 1:30.B. At 2:00.C. At 4:30.听第4段材料,回答第4题。
4. How doe the woman feel?A. Interested.B. Nervous.C. Happy.听第5段材料,回答第5题至第6题。
5. What is the man doing?A. Making an invitation.B. Asking for help.C. Talking about the weather.6. What does the woman need to take for camping?A. A tent.B. Warm clothes.C. Some food.听第6段材料,回答第7题至第8题。
7. What will the speakers do tomorrow evening?A. Watch a film.B. See friends off.C. Put on a show.8. Where will the speakers meet?A. At the airport.B. At the cinema.C. At the cafe.听第7段材料,回答第9题至第11题。
9. Where are the pandas?A. Behind the visitor center.B. On the left of the entrance.C. Near the monkey mountain.10. What do the spoken decide to see first?A. Lions.B. Monkeys.C. Pandas.11. What is the possible relationship between the two speakers?A. Strangers.B. Classmates.C. Guide and tourist.听第8段材料,回答第12题至第14题。
12. Which place are the tourists going to visit tomorrow morning?A. The Palace Museum.B. Tiananmen Square.C. The Temple of Heaven.13. What advice does the guide give to the tourists?A. Taking their passport with them.B. Walking to the Palace Museum.C. Wearing comfortable shoes.14. When will they set out tomorrow morning?A. At 7:00.B. At 9:00.C. At 10:00.听第9段材料,回答第15题至第17题。
15. What did the man do on Saturday morning?A. He stayed in a hotel.B. He went to the beach.C. He did some shopping.16. What was the weather like on Monday?A. Sunny.B. Foggy.C. Rainy.17. What are the speakers mainly talking about?A. Travel plan.B. Holiday.C. outdoor activities. 听第10段材料,回答第18题至第20题。
18. What is the woman doing?A. Doing a survey.B. Taking an interview.C. Making an announcement.19. What i s today’s topic?A. Pets.B. Sports.C. Animal helpers.20. What can Minnie do for the woman?A. Answer the phone.B. Lock the door.C. Open the can.第二节:听下面一段对话,根据题目要求在答题卡相应题号后的横线上写下第21题至第25题的关键信息,此段对话你将听两遍。
阅读下面短文,从各题A、B、C、D四个选项中,选出可以填入空白处的最佳答案。
Tomorrow will be another dayOn my way home from work every evening, there would be a homeless middle-aged man standing by the walkway. He was always 26 smiling, and sometimes almost dancing.Every day after work I would remember to gather any spare 27 , and put it aside. I f l saw him I’d give him the coins. A feeling of 28 would come over me every time I saw him as he looked to feel joyful. Sometimes we would ask each other about our day. His 29 would be the same, “I’m fine. Have a bright day.”I knew what his reply was going to be every time, 30 I would still ask. It31 me of how lucky me that even in his situation of being homeless, he was so cheerful. He 32 me how lucky I was, a single mother of four kids, with a good job to providefor them.Then one day I was called into my boss’s office and was told that I was 33 due to the weak economy (经济). A feeling of worry filled my mind immediately, andfor the rest of that day all I could think about was “how am I going to 34 my family, and how am I going to pay rent?”That day I was very sad and upset on my way home. I 35 forgot to preparesome coins for the homeless man as usual. As I waited for the red light to turn, he walked over with a big smile and asked, “How is everything going?” I told him I lost my job and felt really bad. “OK, I will 36 you a dollar today. Tomorrow will be a nother day,” said the man.I was deeply 37 and burst into tears. I wanted to hug him! That day what the man handed me was more than a dollar bill. He taught me a 38 lesson. Whatever material things are taken from you, no one can take away your 39 to be joyful. Tomorrow will be a bright day and full of 40 .26. A. happy B. shy C. nervous D. careful27. A. time B. food C. change D. water28. A. pity B. pain C. anger D. joy29. A. demand B. answer C. view D. reason30. A. but B. for C. or D. so31. A. satisfied B. frightened C. disappointed D. amazed32. A. informed B. advised C. reminded D. warned33. A. fired B. examined C. questioned D. invited34. A. miss B. support C. trust D. check35. A. still B. once C. even D. always36. A. charge B. find C. show D. give37. A. moved B. hurt C. lost D. relaxed38. A. terrible B. valuable C. hard D. strange39. A. cost B. secret C. stress D. choice40. A. doubt B. regret C. hope D. praise三、阅读理解(共20小题,40分。
2019年北京市第一次普通高中学业水平合格性考试语文试卷及解析
2019年北京市第一次普通高中学业水平考试语文试卷一、文言文阅读(16分)阅读《兰亭集序》,完成各题。
永和九年,岁在癸丑,暮春之初,会于.会稽山阴之兰亭,修禊事也。
群贤毕.至,少长咸集。
此地有崇山峻岭,茂林修竹,又有清流激湍,映带左右,引以为.流觞曲水,列坐其次.。
虽无丝竹管弦之盛,一觞一咏,亦足以.畅叙幽情。
是日也,天朗气清,惠风和畅。
仰观宇宙之.大,俯察品类之盛,所以游目骋怀,足以.极视听之娱,信.可乐也。
夫人之相与.,俯仰一世。
或取诸怀抱,悟言一室之内;或因寄所托,放浪形骸之外。
虽趣舍万殊,静躁不同,当其欣于.所遇,暂得于己,快然自足,不知老之将至;及其所之.既倦,情随事迁,感慨系之矣。
向之所欣,俯仰之间,已为陈迹,犹不能不以之兴怀,况修短随化,终期于尽!古人云:“死生亦大矣。
”岂不痛哉!每览昔人兴感之由,若合一契,未尝不临文嗟悼,不能喻之于怀。
固知一死生为虚诞,齐彭殇为.妄作。
后之视今,亦犹今之视昔。
悲夫!故列叙时人,录其所述,虽世殊事异,所以兴怀,其致一也。
后之览者,亦将有感于斯文。
1. 下列语句中加点词的解释错误..的一项是A. 群贤毕.至毕:全部B. 列坐其次.次:旁边C. 信.可乐也信:任凭D. 人之相与.与:交往2. 下列语句中加点词意义和用法相同的一项是A. 会于.会稽山阴之兰亭当其欣于.所遇B. 亦足以.畅叙幽情足以.极视听之娱C. 仰观宇宙之.大及其所之.既倦D. 引以为.流觞曲水齐彭殇为.妄作3. 下列句子括号中,补充的省略内容不正确...的一项是A. (群贤)会于会稽山阴之兰亭B. 映带(在兰亭的)左右C. 引(清缓溪流)以为流觞曲水D. 每览昔人(对生死)兴感之由4. 对下面两句话的意思,理解都不正确...的一项是①况修短随化,终期于尽②固知一死生为虚诞A. ①何况寿命长短随造化而定,最后一切都化为乌有。
②本来知道无论是生还是死其实都是不可信的。
B. ①何况寿命长短是自然早就安排的,最后一切都会一同消失。
2019年北京市第二次普通高中学业水平合格性考试英语(含答案)
2019年北京市第二次普通高中学业水平合格性考试英语试卷一、听力理解(共25小题,25分。
每小题1分)第一节:听下面十段对话或独白,从各题A、B、C三个选项中,选出能回答问题的最佳答案。
每段对话或独白你将听两遍。
听第1段材料,回答第1题。
1. What is the man looking for?A. An umbrellaB. A teddy bearC. Two keys听第2段材料,回答第2题。
2. Which one is the man's daughter?A B C听第3段材料,回答第3题3. Where does this conversation most probably take place?A. At homeB. In the officeC. In the classroom听第4段材料,回答第4题。
4. What is the man doing?A. Making an apology.B. Making an invitationC. Making an introduction听第5段材料,回答第5题至第6题.5. What will the man buy for his wife?A. A handbagB. A scarf.C. A wallet6. How much will the man pay?A.£2B.£8C.£10.听第6段材料,回答第7题至第8题。
7. What does the woman want to drink?A. CoffeeB. TeC. Juice8. Why does the woman like the sofa?A. Because it's bigB. Because it's traditional.C. Because it's soft听第7段材料,回答第9题至第11题。
9. What room does the man want?A. A single roomB. A double roomC. A quiet room.10. How many nights will the man stay in the hotel?A. One nightB. Two nightsC. Three nights11. What does the man want to do the next morning?A. Drink a coffeeB. Run in the gymC. Have a swim.听第8段材料,回答第12题至第14题。
2022届北京市普通高中学业水平合格性考试第一次英语试卷
2022届北京市普通高中学业水平合格性考试第一次英语试卷一、听力选择题1. What are the speakers doing?A.Driving a car.B.Seeing the sunset.C.Climbing the mountains.2. When will Parker get up tomorrow?A.At 7:30 a. m.B.At 7:00 a. m.C.At 6:30 a. m.3.A.The food tastes differently.B.The man should see a different view.C.The food is worth the price.D.The prices on the menu are ridiculous.4. What does the man advise the woman to do?A.Go home to get the presentation schedule.B.Borrow the presentation schedule from Rachel.C.Borrow some related books to the topic.5. What day is it today?A.Wednesday.B.Friday.C.Sunday.二、听力选择题6. 听下面一段较长对话,回答以下小题。
1. Where can the man get a free wireless Internet connection?A.In his hotel room.B.At the entrance hall.C.Outside the hotel.2. What is the nightly cost for a refrigerator in the man’s room?A.$8B.$12.C.$15.3. How does the man feel about the cancellation fee?A.It’s too high B.It’s reasonable.C.It’s no a hit high.7. 听下面一段较长对话,回答以下小题。
北京市2023-2024学年高二下学期第一次普通高中学业水平合格性考试英语试 卷
北京市2023-2024学年高二下学期第一次普通高中学业水平合格性考试英语试 卷一、听力选择题1.A.Give the cat away.B.Choose a good name for the cat.C.Learn to care for the cat.D.Hide the cat in the dormitory room.2. What is the relationship between the speakers?A.Boss and secretary.B.Teacher and student.C.Doctor and patient.3. What will the woman do today?A.Buy a book.B.Attend a lecture.C.Teach English.4. What does the woman usually do on Saturday morning?A.She works.B.She sleeps late.C.She does exercise.5.A.He wasn’t going to the party at first.B.He didn’t receive the invitation to the party.C.He has been persuaded to join the party.D.He will attend the party after the man leaves.二、听力选择题6. 听下面一段较长对话,回答以下小题。
1. What tea does good to your lungs?A.Green tea.B.Dark tea.C.Black tea.2. How much will the woman pay?A.100 yuan.B.150 yuan.C.200 yuan.7. 听下面一段较长对话,回答以下小题。
2024年北京第一次高中学业水平合格考语文试卷真题(含答案详解)
2024年北京市第一次普通高中学业水平合格性考试语文试卷考生须知1.考生要认真填写考场号和座位序号。
2.本试卷共8页,共五道大题,共16道小题。
第2、3、4、5、6、8、9、12、13、14小题,必须用2B铅笔作答,其余小题必须用黑色字迹的签字笔作答。
3.试题所有答案必须填涂或书写在答题卡的对应位置,在试卷上作答无效。
4.考试结束后,考生应将试卷和答题卡放在桌面上,待监考员收回。
一、本大题共3小题,共14分。
1.在横线上填写原句。
(1)荀子在《劝学》中多处运用比喻的方法说理。
例如“青,,;冰,水为之,而寒于水”,连用两个比喻形象说明了通过学习能超越自我的道理。
(2)白居易在《琵琶行》中运用侧面描写烘托了琵琶曲强烈的艺术感染力,如“东船西舫悄无言,”“凄凄不似向前声,”。
(3)辛弃疾《永遇乐·京口北固亭怀古》中“想当年,,”三句,描述了当年南朝宋武帝刘裕率领军队驰骋中原、气势威猛如虎的情形。
2.下列文学常识的表述,不正确...的一项是()A.《论语》是中国传统文化典籍之一,其中许多观念内涵深刻,影响深远,如“为政以德”“和而不同”“己所不欲,勿施于人”等。
B.《梦游天姥吟留别》是唐代诗人李白的名篇,描绘了诗人在梦中游历天姥山的情景,在浪漫瑰丽的想象中寄寓着深沉的慨叹。
C.《祝福》出自鲁迅的小说集《呐喊》,作品塑造了众多性格鲜明的人物形象,如“老监生”鲁四老爷、“善女人”杨二嫂等。
D.《哈姆莱特》是英国作家莎士比亚的代表作,讲述了丹麦王子哈姆莱特的叔父杀兄娶嫂、篡夺王位,哈姆莱特为父报仇的故事。
3.下列对陶渊明《归园田居》(其一)的理解,不正确...的一项是()A.“少无适俗韵,性本爱丘山”两句,诗人写自己年轻时就没有适应世俗的气质,本性是热爱山林田园的。
B.“误落尘网中”“久在樊笼里”两句,诗人借“尘网”“樊笼”抒发了对官场的厌倦和对田园生活的向往之情。
C.“开荒南野际,守拙归园田”两句写诗人回归田园后在南野开荒,决心持守愚拙本性,不学伪巧,不争名利。
2020年北京市第一次普通高中学业水平合格性考试及参考答案
2020年北京市第一次普通高中学业水平合格性考试化 学 试 卷可能用到的相对原子质量:H 1 C 12 O 16 Na 23 Cl 35.5 Fe 56第一部分选择题(共50分)在下列各题的4个选项中,只有1个选项符合题意。
( 每小题2分,共50分) 1.对抗疫情离不开化学。
下列抗疫物资中,主要成分不.属于..有机物的是2. A.CH 4B.C 2H 4C.CH 3ClD.C 2H 5OH3.下列物质中,属于电解质的是A.FeB.NaClC.稀盐酸D.Na 2SO 4溶液4.当光束通过下列分散系时,能观察到丁达尔效应的是A.KCl 溶液B.Fe(OH)3胶体C.KOH 溶液D.Na 2SO 4溶液5.下列化合物中,含离子键的是A.H 2OB.KClC.Cl 2D.CH 46.下列元素的原子半径最大的是A.NaB.AlC.SiD.Cl化学试卷 第1页(共8页)7.下列关于物质分类的叙述中,不正确...的是 A.H 2SO 4属于酸 B.Ba(OH)2属于碱 C.SO 2属于氧化物D.氨水属于纯净物8.下列关于化学反应与能量的说法中,不正确...的是 A.Al 与盐酸的反应属于放热反应 B.化学反应总是伴随着能量的变化C.当反应物的总能量高于生成物的总能量时,反应向环境放出能量D.Ba(OH)2·8H 2O 与NH 4Cl 的反应属于放热反应 9.下列关于氨气性质的描述中,不正确...的是 A.黄绿色气体B.有刺激性气味C.相同条件下密度比空气的小D.极易溶于水10.2020年5月1日起,《北京市生活垃圾管理条例》正式施行。
下列可回收物中,主要成分属于合金的是A.塑料瓶B.废报纸C.罐头盒D.旧衣服A.氯气B.氯水C.氯化钠D.氯化氢12.一定温度下,在恒容密闭容器中发生反应:2NO 2(g) N 2O 4 (g) 。
当NO 2、N 2O 4的浓度不再变化时,下列说法不正确...的是 A.NO 2全部转化为N 2O 4 B.该反应已达化学平衡状态 C.正、逆反应速率相等,但不等于零 D.容器中气体颜色不再发生变化13.稀土被称为“工业黄金”和“新材料之母”,稀土资源在我国有丰富的储量。
2019年普通高等学校招生全国统一考试(新课标II卷)英语答案解析(正式版)(解析版)
第Ⅰ卷第一部分听力(共两节,满分30分)略第二部分阅读理解(共两节,满分40分)AMy color television has given me nothing but a headache. I was able to buy it a little over a year ago because I had my relatives give me money for my birthday instea d of clothes that wouldn’t fit.I let a salesclerk fool me into buying a discontinued model. I realized this a day later, when I saw n ewspaper advertisements for the se t at seventy-five dollars less than I had paid. The set worked so beautiful when I first got it home that I would keep it on until stations signed off for the night. Fortunately, I didn’t get any channels showing all-night movies or I would never have gotten to bed.Then I started developing a problem with the set that involved static(静电) noise. For some reason, when certain shows switched into a commercial, a loud noise would sound for a few seconds. Gradually, this noise began to appear during a show, and to get rid of it, I had to change to another channel and then change it back. Sometimes this technique would not work, and I had to pick up the set and shake it to remove the sound. I actually began to build up my arm muscles(肌肉) shaking my set.When neither of these methods removed the static noise, I would sit helplessly and wait for the noise to go away. At last I ended up hitting the set with my first, and it stopped working altogether. My trip to the repair shop cost me $62, and the sit is working well now, but I keep expecting more trouble.21. Why did the author say he was fooled into buying the TV set?A.He got an older model than he had expected.B.He couldn’t return it when it was broken.C.He could have bought it at a lower price.D.He failed to find any movie shows on it.22. Which of the following an best replace the phrase “signed off” in paragraph 1?A.ended all their programsB.provided fewer channelsC.changed to commercialsD.showed all-night movies23. How did the author finally get this TV set working again?A.By shaking and hitting itB.By turning it on and offC.By switching channelsD.By having it repaired24. How does the author sound when telling the story?A.CuriousB.AnxiousC.CautiousD.Humorous【答案】21. C22. A[:23. D24. D22.A 词义推测题。
2019年北京学业水平(合格考)测试通知
【导语】会考频道了解整理到,近期,北京各区发布2019第⼆次学业⽔平测试通知,北京的同学们要注意了,⼀起来看看具体事宜吧!海淀区具体要求执⾏《北京市教育委员会关于印发<北京市普通⾼中学业⽔平考试实施办法(试⾏)>的通知》(京教基⼆〔2017〕13号)、《北京市教育委员会关于北京市普通⾼中学业⽔平考试合格性考试有关问题的补充意见》(京教基⼆〔2017〕27号)、《北京教育考试院关于印发北京市普通⾼中学业⽔平考试合格性考试有关⼯作实施⽅案(试⾏)的通知》(京考会考〔2018〕1号)、《北京教育考试院关于做好2019年第⼆次普通⾼中学业⽔平合格性考试的通知》(京考学考合〔2019〕3号)等⽂件。
考试安排市级合格性考试于6⽉24⽇⾄26⽇进⾏,开考九个学科:语⽂、数学、英语、思想政治、历史、地理、物理、化学、⽣物。
区级组织合格性考试两个学科:信息技术、通⽤技术。
2018级普通⾼中在校⽣(现⾼⼀)可报考七科市级科⽬(思想政治、物理除外)和两科区级科⽬,其余考⽣可报考⼗⼀个学科中未合格的科⽬,已合格的科⽬不得再次报考。
注册及报考⼯作(⼀)2018级⾼⼀年级⼊学的普通⾼中在校学⽣的注册信息通过全市中⼩学学籍管理云平台(CMIS)提取,职技类学校未注册的在校学⽣需由学校统⼀注册。
未注册的社会类考⽣须登录北京教育考试院站(),进⼊“2019年第⼆次普通⾼中学业⽔平合格性考试上报考”页⾯,⾃⾏注册新⽤户并填写相关信息,完成上注册。
(⼆)已注册并取得“学考号”的考⽣,须登录报考站,确认注册信息⽆误后按要求选择报考科⽬。
(三)参加原⾼中会考有部分科⽬未通过的考⽣,如需补考,可参加未通过科⽬的合格性考试。
参加合格性考试后,各科⽬考试成绩将以“合格/不合格”呈现。
(四)原⾼中会考科⽬已取得合格及以上成绩者,不得再报考相应科⽬的合格性考试。
其他⼯作凡已在外省市参加会考(学业⽔平考试)并取得⾼中毕业证,只回京参加⾼考的学⽣,持省级教育考试机构会考成绩证明和⾼考报名信息单,于2019年3⽉1⽇⾄5⽉31⽇期间的每周四下午2:00-4:00,到北京教育考试院办理会考成绩核定⼿续。
北京市2019年第一次普通高中学业水平合格性考试语文试卷(附解析)
2019年北京市第一次普通高中学业水平合格性考试语文试卷一、文言文阅读(16分)阅读《兰亭集序》,完成各题。
永和九年,岁在癸丑,暮春之初,会于.会稽山阴之兰亭,修禊事也。
群贤毕.至,少长咸集。
此地有崇山峻岭,茂林修竹,又有清流激湍,映带左右,引以为.流觞曲水,列坐其次.。
虽无丝竹管弦之盛,一觞一咏,亦足以.畅叙幽情。
是日也,天朗气清,惠风和畅。
仰观宇宙之.大,俯察品类之盛,所以游目骋怀,足以.极视听之娱,信.可乐也。
夫人之相与.,俯仰一世。
或取诸怀抱,悟言一室之内;或因寄所托,放浪形骸之外。
虽趣舍万殊,静躁不同,当其欣于.所遇,暂得于己,快然自足,不知老之将至;及其所之.既倦,情随事迁,感慨系之矣。
向之所欣,俯仰之间,已为陈迹,犹不能不以之兴怀,况修短随化,终期于尽!古人云:“死生亦大矣。
”岂不痛哉!每览昔人兴感之由,若合一契,未尝不临文嗟悼,不能喻之于怀。
固知一死生为虚诞,齐彭殇为.妄作。
后之视今,亦犹今之视昔。
悲夫!故列叙时人,录其所述,虽世殊事异,所以兴怀,其致一也。
后之览者,亦将有感于斯文。
1. 下列语句中加点词的解释错误..的一项是A. 群贤毕.至毕:全部B. 列坐其次.次:旁边C. 信.可乐也信:任凭D. 人之相与.与:交往2. 下列语句中加点词意义和用法相同的一项是A. 会于.会稽山阴之兰亭当其欣于.所遇B. 亦足以.畅叙幽情足以.极视听之娱C. 仰观宇宙之.大及其所之.既倦D. 引以为.流觞曲水齐彭殇为.妄作3. 下列句子括号中,补充的省略内容不正确...的一项是A. (群贤)会于会稽山阴之兰亭B. 映带(在兰亭的)左右C. 引(清缓溪流)以为流觞曲水D. 每览昔人(对生死)兴感之由4. 对下面两句话的意思,理解都不正确...的一项是①况修短随化,终期于尽②固知一死生为虚诞A. ①何况寿命长短随造化而定,最后一切都化为乌有。
②本来知道无论是生还是死其实都是不可信的。
B. ①何况寿命长短是自然早就安排的,最后一切都会一同消失。
2021年北京市第一次普通高中学业水平合格性考试试卷和答案
A.核糖体B.内质网C.细胞核D.线粒体
3.右图是三个相邻植物细胞之间水分流动方向示意图。图中三个细胞的细胞液浓度关系是
A.甲>乙>丙
B.甲<乙<丙
C.甲>乙,乙<丙
D.甲<乙,乙>丙
4.细胞内葡萄糖分解为丙酮酸的过程
A.不产生CO2
B.必须在有O2条件下进行
25.可以与动物细胞的吞噬泡融合,并消化掉吞噬泡内物质的细胞器是
A.线粒体B.溶酶体C.高尔基体D.内质网
26.细菌被归为原核生物的原因是
A.细胞体积小B.单细胞C.没有核膜D.没有DNA
27.《晋书·车胤传》记载了东晋时期名臣车胤日夜苦读,将萤火虫聚集起来照明读书的故事。萤火虫尾部可发光,为发光直接供能的物质是
A.一条染色体复制形成的两条染色体B.减数分裂过程中配对的两条染色体
C.形态特征大体相同的两条染色体D.分别来自父方和母方的两条染色体
10.右图为某动物细胞分裂的示意图。该细胞处于
A.有丝分裂中期
B.有丝分裂后期
C.减数第一次分裂后期
D.减数第二次分裂后期
11.某生物的精原细胞含有42条染色体,在减数第一次分裂形成四分体时,细胞内含有的染色单体、染色体及其上的DNA分子数依次是
A.抑制DNA的合成,细胞将停留在分裂期
B.细胞周期分为前期、中期、后期、末期
C.细胞分裂间期为细胞分裂期提供物质基础
D.成熟的生殖细胞产生后立即进入下一个细胞周期
8.鸡在胚胎发育早期趾间有蹼状结构,随着胚胎的发育,蹼逐渐消失的原因是
A.细胞增殖B.细胞衰老C.细胞坏死D.细胞凋亡
9.同源染色体是指
