Current location - Education and Training Encyclopedia - Educational Knowledge - Who has a history paper for the first grade?
Who has a history paper for the first grade?
Test questions of unit 1 and unit 2 of the first grade history (Volume 1).

Examination scope: The examination time of Unit 1 and Unit 2 is 60 minutes, and the total score of the examination paper is 100.

Students, welcome you into the hall of history! Speaking of history, it seems far away from us, but if you really go into history, you will find that it is closely related to our lives. It can bring you fun, make you smart, tell you a lot about being a man and give you a chance to show yourself. Students, in these two months of study, you must have gained a lot of harvest and experience. Walk smartly into the history exhibition room and show your beautiful style!

1. Can you choose the most convincing one? Please fill in the answers in the table below, with 2 points for each question, totaling 50 points.

1 and1In May 1965, archaeologists in China discovered two fossils of front teeth and some rough stone tools in a county in Yunnan Province. Chinese Academy of Geological Sciences determined that they were about 6.5438+0.7 million years ago by paleomagnetic method. This is the earliest known human in our country.

A, Yuanmou person B, Beijinger C, caveman D, Banpo person

2. The ancient residents who once lived near Beijing today were ① Yuanmou, ② Beijingers and ③ cavemen.

a、①② B、①③ C、②③ D、①②③

2. "Living about 700,000 years ago, I still have some characteristics of apes, but I have a clear division of labor between my hands and feet, and I can make and use tools, and I have been able to use natural fire." According to these characteristics, please judge that he belongs to.

A, Yuanmou B, Beijingers

C, Neanderthal D, Banpo Primitive Man

3. If you were an original resident living in the Yangtze River valley about 7,000 years ago, which of the following phenomena could you not see?

The rice in the farmland is growing well. B, people use cultivated land on wasteland.

C, dry column houses strewn at random have send, D, bronzes beautifully made.

4. Who was the earliest original inhabitant who planted rice in the world?

A, Neanderthals B, Banpo aborigines

C, Hemudu indigenous inhabitants D, Dawenkou indigenous inhabitants

5. Which of the following tribal alliance leaders is regarded as "the ancestor of mankind" by later generations?

A, Yan Di B, Huangdi C, Chiyou D, Dayu

6. In China's myths and legends, after the Yellow Emperor, three famous figures, Yao, Shun and Yu, appeared in the Yellow River basin, and they all became the leaders of tribal alliances by recommendation. Historically, this method of cultivating leaders has been called

A. Electoral system B. Voting system

C, hereditary system D, abdication system

7, the end of the primitive society, the beginning of the slave society is

First, the battle between the two deer, the establishment of the Xia Dynasty

C, the implementation of abdication system D, the formation of the Chinese nation

8, the founder of the first dynasty in Chinese history is?

A, Tang B, Huangdi C, Yu D, Shun

9. In July this year, at the 29th World Heritage Conference held in South Africa, the Yinxu site in Henan was listed as the deliberation item of the 30th World Heritage Conference in 2006. Do you think the main reason why Yin Ruins were declared as a world cultural heritage is that it showed people the social features of which dynasty in ancient China?

A, Xia Dynasty B, Shang Dynasty C, Western Zhou Dynasty D and Eastern Zhou Dynasty

10, in order to consolidate the rule, the rulers of the Western Zhou Dynasty implemented the system of enfeoffment. After that, a strict hierarchy was gradually formed. One of the highest grades is

Doctor A, B, C, D and Qing

1 1, look carefully at the picture below. What do you think is the largest bronze found in the world at present?

A B C D

12, the following options are wrong.

First, compared with the tyrant Sun Jie

B, 65438 BC+0600 BC, soup destroyed summer, built business.

In 770 BC, Zhou Pingwang moved to the East, known as the Eastern Zhou Dynasty.

D. The last king of the Western Zhou Dynasty was Zhou Youwang.

13. Regarding agriculture and animal husbandry in Xia, Shang and Zhou Dynasties, the following statement is wrong.

First, agriculture and animal husbandry have been quite developed.

Agriculture already knows about seed selection, fertilization and pest control.

C today, the main varieties of poultry and livestock have been in the Shang dynasty.

D, Western Zhou agriculture has used a large number of bronze farm tools for production.

14, The Analects of Confucius said: "Guan Zhong is the public and the tyrant, conquering the world." What historical facts does this material reflect?

A, Jin Wengong dominates B, Qi Huangong dominates C, Gou Jian dominates D and Chu Zhuangwang dominates.

15, which of the following is the main reason for the situation of a hundred schools of thought contending?

A, the prosperity of private schools B, the annexation war of vassal States

C, social change D, the liberation of scholars

16, "Confucius knows his students very well. He knows that Gao Chai is dull, has been dull, Zhang Zi is extreme, and Luz loves impulsiveness, so he educates them in a targeted manner, gives play to their strengths, and helps them overcome their shortcomings. " The most accurate understanding of this sentence is

A, educating people with "morality" B, teaching without distinction.

C, teach students in accordance with their aptitude, from each according to his ability.

17, the most precious musical instruments unearthed in Suixian County, Hubei Province are

A, chime B, bronze bell C, seven-hole bone flute D, ceramic jewelry box

18, which of the following four warring States countries is located at the easternmost end?

A, Chu B, Qi C, Qin D, Yan

19, our ancestors determined that there were 24 solar terms in a year.

A, Xia Dynasty B, Shang Dynasty C, Spring and Autumn Period D, Warring States Period

20, China's written history began in

A, Western Zhou Dynasty B, Shang Dynasty C, Spring and Autumn Period D, Warring States Period

2 1. Pursuing and establishing a harmonious and stable society is the tradition of the Chinese nation. Mozi's thought of embodying this feature is

A, "happiness, disaster depends on; Unfortunately, the blessing. "

B, "universal love" and "no attack"

C, "Don't do to others what you don't want others to do to you"

D, "the benevolent loves others" and "ruling the country by virtue"

22, the following statement, the incorrect one is

Han Feizi was a representative figure of Legalists in the Warring States Period.

B, Lao Tzu is the founder of the Taoist school.

C. Sun Wu's book is The Art of War.

D, Zhuangzi put forward the theory of "benevolence"

23. During the Warring States Period, the most important influence of state reform was

First, crack down on slave owners and nobles

B, improve the social status of farmers

C. Promoting economic development

D, the feudal system was gradually established through political reform.

24. In Qin State at the end of the Warring States Period, if a farmer wants to be exempted from labor and punishment, the best way should be

1. Being a soldier and making military achievements; B, don't hide illegal behavior.

C, legal business to get rich D, mass production of grain and cloth.

25. The narrative about Dujiangyan is correct.

Li Bing of Qin in the Spring and Autumn Period; ② Located in the middle reaches of Minjiang River; (3) the famous water transport project; (4) eliminate floods and irrigate farmland.

a①③④B②③④C①②④D②④

Second, the medical history clinic judged right or wrong (please judge whether the following statement is correct, fill in the brackets after the question, draw "√" correctly, and draw "×" wrongly. 1 point for each question, totaling1point)

1. The difference in eating habits between the north and the south of China was formed as early as six or seven thousand years ago. ( )

2. The Xia, Shang and Zhou Dynasties were the bronze age in China, so the earliest bronzes in China appeared in the Xia Dynasty.

3. During the Spring and Autumn Period and the Warring States Period, the five tyrants in the Spring and Autumn Period and the seven heroes in the Warring States Period coexisted. ( )

4. The battles of Changping, Guiling and Chengpu were all famous battles in the Warring States Period. ( )

5. The Art of War written by Sun Wu at the end of the Spring and Autumn Period is the earliest art book in the world. ( )

6. "Long breath, tears can't be hidden!" From Qu Yuan's lyric poem Li Sao. ( )

7. The story of the idiom "Avoid Three Houses" happened during the hegemony war between Qin Chu and China. ( )

8. There are many kinds of bronzes in the Western Zhou Dynasty, which are widely used for sacrifice. ( )

9. In order to consolidate the rule, the rulers of the Eastern Zhou Dynasty began to implement the enfeoffment system. The Emperor of Zhou gave land, civilians and slaves to relatives and heroes and made them princes. ( )

10, the historical events reflected in the following figure mark the establishment of the Western Zhou Dynasty. ( )

Third, material analysis questions and problems. (This question has a total of 40 points)

1, (16 points) Read the following materials and answer the questions.

"If you don't rule the world together, the country will be illegal and ancient" —— Historical Records quoted Shang Yang's words.

Please answer:

(1) When and with whose support was Shang Yang's political reform carried out? (2 points)

(2) According to your judgment, which school does Shang Yang represent? (2 points)

(3) What is the main content of Shang Yang's political reform? (8 points)

(4) What influence did Shang Yang's political reform have on Qin? (4 points)

2.( 1 1) Read the following pictures and complete the form with relevant knowledge (3 marks will be affected, the rest will be 1).

The first volume of the first grade history is a multiple-choice exercise.

1. The following ancient human sites are located in the Yangtze River basin.

A. Neanderthal B. Yuanmou C. Lantian D. Beijinger

2. The fundamental difference between humans and animals is that

3. In the process of evolution from apes to humans, the decisive factor is

A. food B. evolution of limbs C. evolution of brain D. labor

4. The typical representative of clan settlement in the Yellow River Basin is

A. Banpo settlement B. Original inhabitants of Dawenkou C. Hemudu settlement D. Neanderthals

5. In matrilineal clan communes, women are respected because they:

A is good at hunting and fishing, B is gentle, C is the organizer of life and production, and D is kind-hearted.

6. China people call themselves "descendants of the dragon". The image of the dragon highlights.

A Chinese people are good at imagining B Chinese people are made up of different tribes.

C. The enterprising spirit of the Chinese nation D. The tradition of unity and friendship of the Chinese nation

7. When the legendary tribal alliance leader came to power, the primitive society in China had come to an end: A, Yao, B, Shun, C and Yu, D.

8. The first slave country in the history of our country was established in the Xia Dynasty ()

A.265438+ 0 century BC 65438+ 6 century BC 265438+ 0 century BC 65438+ 6 century BC

9. Which of the following systems does not conform to the situation of the Western Zhou Dynasty () A abdication system B hereditary system C enfeoffment system D hierarchy?

10. During the Warring States period, individual small farmers gradually became the basic production unit of society. The main reasons for this situation are: (a) the wars of various vassal States during the Spring and Autumn Period and the Warring States Period; And (b) the disintegration of the enfeoffment system.

C. The use and promotion of iron and Niu Geng D. The emerging landlord class has stepped onto the historical stage.

1 1. During the Warring States period, the person who advocated "universal love" and "non-attack" and hoped that people would help each other and love each other was ().

In 12 and Five Overlords in the Spring and Autumn Period, the strategy of "respecting the king and rejecting foreign countries" is dominant:

A, Qi Huangong B, Jin Wengong C, Qin Mugong D, Chu Zhuangwang

13. What was the slave society in China during the Spring and Autumn Period? The formation of a and b, the development of c, the prosperity and disintegration of d.

14, China invented pig iron smelting technology in A, Chunqiu B, Warring States C, Qin D and Western Han Dynasty.

15, put forward the proposition of establishing a feudal country with absolute monarchy and centralization during the Warring States Period;

A, Lao Zi B, Mencius C, Zhuangzi D, Han Feizi

16, the most useful theory for feudal rulers in the Warring States period is:

A Confucian b Mohist c Taoist d Legalist

17. The first slavery dynasty in Chinese history was A. Xia Dynasty B. Shang Dynasty C. Western Zhou Dynasty D. Eastern Zhou Dynasty.

18. According to legend, the person who divided the whole country into "Kyushu" was () A. Kai B. Yu C. Yao D. Shun.

19, the founding fathers of the western Jin dynasty are: a Si Mazhao b Sima Qian c Sima Yan d Sima yi.

20. About BC 1300, the Shang king who moved to Yin was A. Shang Tang B. Pan Geng C. Shang and Zhou D. Xia Jie.

2 1. The founder of the Western Zhou Dynasty is () A. Zhou Wenwang B. Zhou Wuwang C. Zhou Youwang D. Zhou Pingwang.

22. Regarding the Xia, Shang and Western Zhou Dynasties, the following measures were taken to fight against foreign countries and suppress resistance at home, including ()

① Army ② Criminal Law ③ Education ④ Etiquette education A.234b.134c.124d.123.

23. Among the five tyrants in the Spring and Autumn Period, the first hegemony was A. Qin Mugong, B. Jin Wengong, C. Qi Huangong and D. Chu Zhuangwang.

24. The following allusions are related to Chu Jin's hegemony: () A. An old horse knows the way B. Retreat three homes C. Eat your bread and taste your courage D. Respect the king and be busy with foreigners

25. The following allusions are related to wuyue's hegemony in the late Spring and Autumn Period ().

A. respect the king and resist foreign aggression. B. stay away from miyake. C. eat your bread and taste your courage. D. talk on paper

26, the following historical events or allusions related to the idiom "sooner or later" is ()

A. Encircling Wei to save Zhao B. On paper C. Reliance on salary and courage D. "Combination" and "Lian Heng"

27. the vassal state that won the central plains was () a.qi.b.chu.c.jin.d.qin.

28. At present, the largest bronze found in the world refers to ().

29. Dujiangyan built by Li Bing is located in () A. Yellow River Basin B. Minjiang River Basin C. Huaihe River Basin D. Liaohe River Basin.

30. The school that advocates "governing by doing nothing" is ()

3 1. The dynasties called Yin by later generations were A Xia, B Shang, C Western Zhou and D Eastern Zhou.

32. The measures of Shang Yang's political reform have the most far-reaching influence on later generations.

A, unified measurement b, military c, production d, county system.

33. Qin became the most powerful country among the Seven Heroes of the Warring States, mainly because.

A more use of iron farm tools, B implementation of Shang Yang Reform, C emphasis on water conservancy construction, D promotion of Niu Geng. Which of the following is the main reason for the contention of a hundred schools of thought?

A, the prosperity of private schools B, the annexation war of vassal states C, the great social changes D, the liberation of scholars.

35. The appearance of writing is a sign that human beings have entered a civilized era. Our text today comes from

A bronze inscription b small seal c Oracle Bone Inscriptions d pottery symbol.

36. The most accurate statement of Dujiangyan's function is: A flood control and drainage B flood control and water storage C flood control and irrigation D water storage and drought prevention.

37. Many governors in the Western Zhou Dynasty were produced by (): A. Slavery B. Hereditary system C. Feudal system D. Concession system.

38. The orthodoxy of China's feudal culture for more than 2,000 years is: A. Taoism B. Mohism C. Confucianism D. Legalism.

39. The era of slavery civilization in China began in: A, Huangdi period B, Yu period C, Qi period D and Tang period.

40. Which of the following systems does not conform to the situation of the Western Zhou Dynasty: A, abdication system B, hereditary system C, enfeoffment system D, and hierarchical system.

4 1. During the Spring and Autumn Period, the vassal states that competed with Jin in the Central Plains were: A, Qi B, Wu C, Chu D and Qin.

42. The era of slave civilization in China began in: A, Huangdi period B, Yao period C, Yu period D and Tang period.

43. The following statement is incorrect:

First, Oracle Bone Inscriptions is quite mature. B, Jinwen is more standardized than Oracle Bone Inscriptions.

C, bamboo slips and silk script D appeared in the Spring and Autumn Period, and big seal script appeared in the late Western Zhou Dynasty.

44. King Pan Geng of Shang Dynasty moved his capital to: A, Yangcheng B, Bo C, Yin D and Haojing.

45. In 356 BC, the monarch who began to appoint Shang Yang was:

A, Qin Mugong B, Qin Xiaogong C, Qin Shihuang D, Qi Huangong

46. Who said the military motto "He who knows the other is invincible": A, Mozi B, Sun Wu C, Sun Bin D, Xunzi?

47. During the Warring States Period, Zhang Yi of Qin State and Gongsun Yan of Wei State belonged to: A Confucian, B Legalist, C Military Strategist and D Taoist.

48. Among the following vassal states, () is one of the "Five Overlords in the Spring and Autumn Period" and "Seven Heroes in the Warring States Period".

A. qi b Jin c Wu d yue Guo

49. During the Spring and Autumn Period, the remarkable improvement of social productivity was:

A, the use of ironware b, the promotion of Niu Geng c, the increase of private land d, the construction of water conservancy.

50. The recorded history of China begins with: A, Yao Shunyu Period B, Xia Dynasty C, Shang Dynasty D and Western Zhou Dynasty.

5 1, the starting and ending points of Qin Changcheng are:

52. The battles between Liu Bang and Xiang Yu for the throne include: the battle of A Julu, the battle of B Changping, the battle of C Chu and Han, and the battle of D Chengpu.

53. The following emperors are quite different from Qin Shihuang's attitude towards Confucianism.

A Emperor Gaozu B Guangwudi C Zhou Wenwang D Hanwudi

54. After the unification of Qin Dynasty, the standard script used in the whole country was A. Oracle Bone Inscriptions B. Jinwen C. Xiaozhuan D. Lishu.

55. Qin Shihuang built the Great Wall for the purpose of ()

A, in order to northern expedition Xiongnu B, to show imperial power C, to resist Xiongnu D, to unify the whole country.

56. In which emperor period did the unification of the Western Han Dynasty appear? A. Emperor Gaozu B. Wendi C. Jingdi D. Emperor Wu

57, Xinjiang officially belongs to the central governance began in ().

Answer? 65438 BC+038 BC? 127 C BC? 65438 BC+60 BC

58. In the peasant war at the end of the Qin Dynasty, the battles that played a decisive role in overthrowing the rule of the Qin Dynasty were:

A, the battle of Changping B, the battle of Julu C, the battle of Chengpu D, and the battle of Maling

59. The decisive battles of Qin's unification of the six countries are: A, Battle of Guiling B, Battle of Maling C, Battle of Changping D and Battle of Julu.

60. The first unified centralized feudal country in the history of China was () A. Xia Dynasty B. Warring States Period C. Qin Dynasty D. Western Han Dynasty.

6 1.a, Chen Sheng B, Guangwu C, Xiang Yu D and Liu Bang overthrew the Qin Dynasty and established the Western Han Dynasty.

62, the following measures belong to Qin Shihuang is ()

A. build the great wall b, set up the county c, use the square hole d, and stipulate that the supreme ruler is called the emperor.

63. The main purpose of Qin Shihuang's "burning books to bury Confucianism" is ()

A. establish the image of Qin B. strengthen ideological control C. restrict people's speech D. prohibit the spread of Confucianism

64. The most fundamental influence of the tyranny of the Qin Dynasty on society is ()

A. class contradictions are sharp B. political turmoil C. people's lives are miserable D. productivity is seriously damaged

65. Shout: "Which do you prefer, princes and princes?" The slogan of the uprising is:

A, Chen Sheng B, Guangwu C, Xiang Yu D, Liu Bang

67. Some people suggested to Emperor Wu of the Han Dynasty that "a hundred schools of thought should be deposed and Confucianism should be respected exclusively": A, Xiao He B, Han Xin D and Dong Zhongshu.

68. Emperor Wu of the Han Dynasty accepted the suggestion of () when he promulgated the "favor order". A Dongzhongcun B Liu Ying C Chao Cuo D Zhufuyan

69. In BC 1 19, the army defeated the Huns: A Dou Gu, B Dou Xian, C Wei Qing, Huo Qubing D Meng Tian.

70. The reason why Emperor Wu of the Han Dynasty fought back against the Huns was:

(1) Economic prosperity and strong national strength; ② Consolidate the Western Han regime; (3) annexing the Huns; (4) Ensure peace in the northern border counties.

A ①②③ B ②③④ C ①②④ D①③④

7 1, the pioneer of traffic between the central plains and the western regions is (). Answer? Wei Qing B? Huo Qubing C? Zhangqian d? Wang zhaojun

72. The story of "Zhaojun's Embarkation" takes place in: A Emperor Yuan of the Eastern Han Dynasty, B Emperor Han Wudi of the Eastern Han Dynasty, C Emperor Wendi of the Western Han Dynasty and D Emperor Wu of the Western Han Dynasty.

73. During the Western Han Dynasty, the emperors who sent Zhang Qian to the Western Regions twice were: A Han Wendi B Han Jingdi C Han Yuandi D Han Wudi.

74. The earliest papermaking techniques in China began in: () A, Qin Dynasty B, Early Western Han Dynasty C, Early Eastern Han Dynasty D and Three Kingdoms Period.

75. The medical books that laid the foundation of TCM therapeutics in China are: ()

A, Treatise on Febrile Diseases B, Shennong Herbal Classic C, Huangdi Neijing D, Compendium of Materia Medica

76. The general history of China's first biography is: A Hanshu B Shiji C Lun Heng D Lun Shen.

77. The time when Buddhism was introduced into the Central Plains of China was () A. Early Western Han Dynasty B. Late Western Han Dynasty C. Early Eastern Han Dynasty D. Late Eastern Han Dynasty

78. Taoism is a native religion in China, which rose in the Warring States Period, the Qin Dynasty, the Western Han Dynasty and the Eastern Han Dynasty.

79, papermaking is one of the great inventions of working people in ancient China, writing and painting paper appeared in:

A late eastern Han dynasty b late western Han dynasty c early western Han dynasty d early Qin dynasty

80. The doctors who manufacture the anesthetic "Mafeisan" are: A Bian Que B Zhang Zhongjing C Hua Tuo D Li Shizhen.

8 1, at the end of the Eastern Han Dynasty, the main purpose of Cao Cao's offering to the Han Emperor Xu Wen 'an was:

A revitalizes the Han dynasty, B is loyal to the imperial court, C wins the hearts of the people, and D holds the emperor to make the princes.

82. It was () that Cao Jun laid the foundation for unifying the northern campaign.

A. Battle of Julu B. Battle of Changping C. Battle of Guandu D. Battle of Red Cliffs

83, AD 208, contributed to the formation of the Three Kingdoms battle is:

A Battle of Changping B Battle of Julu C Battle of Guandu D Battle of Red Cliffs

84. During the Three Kingdoms period, the first emperor was: A Cao Cao B Sun Quan C Cao Pi D Liu Bei.

85. An important battle to lay the foundation for the formation of the tripartite confrontation pattern among the three countries ()

A. Battle of Julu B. Battle of Guandu C. Battle of Battle of Red Cliffs D. Battle of Feishui

86. The founder of Wei State is () A. Cao Cao B. Cao Pi C. Liu Bei D. Sun Quan.

87. In the battle of Guandu, the main reason for Cao Cao's victory was ()

A. Soldiers have enough food and grass. B. Tactics are appropriate. C. Political advantages. D. Win people's hearts.

88, the battle of Guandu and Battle of Red Cliffs, the defeated party's subjective common reasons are:

A is arrogant and underestimates the enemy, B is distracted, C is not fully prepared, and D does not learn water warfare.

89. During the Three Kingdoms period, the fleet of Wu arrived in Yizhou, which is today: A Macau B Taiwan Province Province C Japan D India.

90. Among the following works, Li Daoyuan's works are: ()

9 1 During the Eastern Jin Dynasty and the Southern Dynasties, there were two main reasons for the economic development in the south of the Yangtze River: ① a large number of northerners went south; ② Superior natural conditions in the south.

(3) Southern rulers attach great importance to agricultural production (4) There is no war in the South ()

a、①② B、②③ C、③④ D、①④

92. The correct sequence of the following famous battles is () ① Battle of Julu ② Battle of Guandu ③ Battle of Red Cliffs ④ Feishui A.1234b.4321C.1324d.2314.

93. Which of the following ethnic minorities established the Northern Wei Dynasty () A. Clan B. Xianbei C. Qidan D. Xiongnu?

94. The author of China's first complete agricultural book Qi Yao Min Shu is ().

95. The climax of the first great migration in ancient China appeared in ().

A. the last years of the eastern Han dynasty B. the last years of the three kingdoms C. the early years of the western Jin dynasty D. the last years of the western Jin dynasty

96. The most important factor in the development of Jiangnan area is ().

A southern production tools are advanced, b southern natural conditions are better, c northern farmers move southward in large numbers, and d southern rulers stone.

97. The statement about the Battle of Feishui is incorrect:

With the support of ministers and soldiers and civilians, Afujian led an army to attack Jin. It happened in 383 AD.

C The Eastern Jin Dynasty defeated the former Qin Dynasty D, which was a famous battle to win more with less.

In the 98th century and the early 5th century, the minority regimes that unified the Yellow River Basin were: A Pre-Qin, B Northern Wei, C Western Jin and D Northern Zhou.

99, the fundamental purpose of emperor xiaowen's reform is:

A restores the agricultural production in the north, b accelerates the great integration of the northern nationalities, c consolidates the rule of the Northern Wei Dynasty, and d accepts the advanced culture of the Han nationality.

100, the main background to promote the reform of Emperor Xiaowen in the Northern Wei Dynasty is:

A. the emergence of the trend of great ethnic integration B. the support of ministers C. the recovery and development of the northern economy D. the uprising of the people of all ethnic groups