模拟试题[8] Simulated test Part I Structure and Vocabulary Directions: Beneath each of the following sentences, there are four choices marked A, B, C, and D)Choose the one that best completes the sentence. Mark your answer on the ANSWER ShEET by blackening the corresponding letter in the brackets. (5 points) the many hours of study that he devoted to the sub ject, he still found the subject matter difficult A)After B) D)Despite 2. Tell me how to send a e il to my friends in the United States, A)don' B)do W D)shall you 3. Since the ake part in the governme to help t of the public costs. A)be taxed B)to be taxed C)being taxed 4. What they wanted to know was when and where the 36th International Field Emission Abe hele B)to be held C)is to be held be held is the mechanism of high temperature superconductivity Awhich cont B)on which there continues to be intense debate
模拟试题[8] Simulated Test [PREVIOUS] [NEXT] Part I Structure and Vocabulary Section A Directions： Beneath each of the following sentences,there are four choices marked A,B,C,and D)Choose the one that best completes the sentence.Mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets.(5 points) 1. _____ the many hours of study that he devoted to the subject, he still found the subject matter difficult. A)After B)Because of C)Due to D)Despite 2. Tell me how to send a E mail to my friends in the United States, _____ . A)don′t you B)do you C)will you D)shall you 3. Since they could not vote or take part in the government, they resented _____ to help pay most of the public costs. A)be taxed B)to be taxed C)being taxed D)taxed 4. What they wanted to know was when and where the 36th International Field Emission Conference _____ . A)be held B)to be held C)is to be held D)was to be held 5. Subject _____ is the mechanism of high temperature superconductivity. A)which continues to be intense debate. B)on which there continues to be intense debate
C) D)what continues to be intense debate debate for the rich oil resources, life would be a perpetual struggle against poverty fo the people in the Middle eastern countries A)If it shouldn'tbe B)Had it not bee was no t D)Were it ne 7. Some stories set us thinking ve should do under similar circumstanc A)which D)tha 8. During the World War II his father a living. How could he send his three children to school? A) could not even make B)could note even make C)even could not make D)could even not make the history of the tough, strong willed Nebraska farmer. A)Not only is much of the history of Nebraska B)Although it is much of the history of Nebraska that is C)It is as much the history of Nebraska's being D)Much of the history of Nebraska is 10. The mini bus production line by the end of this ye A)Will be automated B) C)will have been automated D)would be automated Section b Directions: Each of the following sentences has four underlined parts marked A, B, C, and D)Identify the part of the sentence that is incorrect and mark your answer on the ansWer Sheet by blackening the corresponding letter in the brackets. (5 points 11. All of us have read thrilled (A)stories in which (B)the hero had only a limited(c) and specified time to live.(D) 12. New dictionaries are needed (A) because English has changed (B)more (C)in the past two generations than any other time (D) in its history
C)on which it continues to be intense debate D)what continues to be intense debate debate 6. _____ for the rich oil resources, life would be a perpetual struggle against poverty for the people in the Middle Eastern countries. A)If it shouldn′t be B)Had it not been C)If it was not D)Were it not 7. Some stories set us thinking, _____ we should do under similar circumstances. A)which B)wonder what C)wondering what D)that 8. During the World War Ⅱ his father _____ a living. How could he send his three children to school? A)could not even make B)could note even make C)even could not make D)could even not make 9. _____ the history of the tough, strong willed Nebraska farmer. A)Not only is much of the history of Nebraska B)Although it is much of the history of Nebraska that is C)It is as much the history of Nebraska′s being D)Much of the history of Nebraska is 10. The mini bus production line _____ by the end of this year. A)Will be automated B)were automated C)will have been automated D)would be automated Section B Directions: Each of the following sentences has four underlined parts marked A,B,C, and D) Identify the part of the sentence that is incorrect and mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets. (5 points) 11. All of us have read thrilled (A) stories in which (B) the hero had only a limited (C) and specified time to live. (D) 12. New dictionaries are needed (A) because English has changed (B) more (C) in the past two generations than any other time (D) in its history
13. A weI tten (A)composition calls in (b)good choice of words ( C)and clear organization among(D)other things 14. I should want (A) to see the people whose (B)kindness, gentleness and companionship have madc(C)my lifc worthy living(D) 5. The field of dynamics in physics is concerned (A)with a particle's motion(B)in relation 16. How (A) native Americans developed corn is a puzzling,(B)for no wild corn has ever been (c)discovered, and it grows only where (D)people plant and tend it 17. In many pieces of music there is (a)dominant theme on which(b)the restful (C)of the composition is centered. (D) 18. A loudspeaker functions on(A)the same(B)principle that the telephone receiver does. but is more (C) larger and louder.(D) 19. A sandy hair girl(A) is needed(B)to play the part of (C) the reporter in this(D)new 20. Reducing the inefficiencies(A) in production lines (B)were (C) the main concern of the newly hired (D) consultants Section c Directions: Beneath each of the following sentences, there are four choices marked A, B, C, and D) Choose the one that best completes the sen tence. Mark your answer on the anSWer ShEeT by blackening the corresponding letter in the brackets. (10 points) 21. I' m not sure why he didn't go into the higher class, but I he failed the entrance test B)suspect C)predict D)deduce 22. An application to join this scheme places you under no obligation A B)eventually D)what soever A fire alarm in the adjoining building caused the play at the theater to be A)broken away B)b C)broken down D)broken out
13. A well written (A) composition calls in (B) good choice of words (C) and clear organization among (D) other things. 14. I should want (A) to see the people whose (B) kindness, gentleness and companionship havc madc (C) my lifc worthy living (D) . 15. The field of dynamics in physics is concerned (A) with a particle′s motion (B) in relation (C) to the forces acting it. (D) 16. How (A) native Americans developed corn is a puzzling, (B) for no wild corn has ever been (C) discovered, and it grows only where (D) people plant and tend it. 17. In many pieces of music there is (A) dominant theme on which (B) the restful (C) of the composition is centered. (D) 18. A loudspeaker functions on (A) the same (B) principle that the telephone receiver does, but is more (C) larger and louder. (D) 19. A sandy hair girl (A) is needed (B) to play the part of (C) the reporter in this (D) new play. 20. Reducing the inefficiencies (A) in production lines (B) were (C) the main concern of the newly hired (D) consultants. Section C Directions: Beneath each of the following sentences, there are four choices marked A,B,C,and D) Choose the one that best completes the sentence. Mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets.(10 points) 21. I'm not sure why he didn′t go into the higher class, but I _____ he failed the entrance test. A)estimate B)suspect C)predict D)deduce 22. An application to join this scheme places you under no obligation _____ . A)indeed B)eventually C)apart D)whatsoever 23. A fire alarm in the adjoining building caused the play at the theater to be _____ . A)broken away B)brokcn off C)broken down D)broken out
t buy the book with A)without B)with D) 25. He was extremely tired, but he wa unable to sleep until after midnight. B) re frightened by oncept that they in their own mind B)accepte 27. The second law of thermodynamics says, that heat never flows spontaneously from A)in the effe B)in effe D)at the effect 28. The international Olympic Committee the rules for athletes in the olympic Games A) B)I D)lays off 29. Al though they usually did their own painting and papering, on this occasion they brought A)insi B)interic C)internal 30. Automation threatens mankind with an increased number o hours A)us B 31. The staff at the hospital were well to deal with th
24. You must buy the book with your own pocket money or do _____ . A)without B)with C)away with D)up 25. He was extremely tired, but he was _____ unable to sleep until after midnight. A)nevertheless B)otherwise C)meanwhile D)whereas 26. They were frightened by a concept that they _____ in their own mind. A)sought B)accepted C)created D)idealized 27. The second law of thermodynamics says, _____ , that heat never flows spontaneously from a cooler to a hotter object. A)in the effect B)in effect C)at effect D)at the effect 28. The international Olympic Committee _____ the rules for athletes in the Olympic Games. A)lays down B)lays aside C)lays out D)lays off 29. Although they usually did their own painting and papering, on this occasion they brought in a firm of _____ decorators. A)inside B)interior C)internal D)inward 30. Automation threatens mankind with an increased number of _____ hours. A)useless B)active C)idle D)complex 31. The staff at the hospital were well _____ to deal with the epidemic. A)capable
D) 32. This course no previous knowledge of the sub ject. B D)assembles 33. The specialist recommended that the exact nature of the womans illness should be kept her A)from C)back from D 34. The introduction of fabrics made from rayon, ny lon and other fibers has made many changes in our civilization. A)magi B)arithmetic C)manufactured 35. Having decided to go abroad, he at once set fulfilling his business in China. A)down B)in 36. Even on week end, Mrs. Watson prefers doing something doing nothing. B) C)rather than D)instead of 37. They were very disappointed the findings of the Commission. B) c) D)of 38. I ordered a lock in amplifier two weeks ago, and i think it that i will have A)pos B)probable
B)equal C)ready D)equipped 32. This course _____ no previous knowledge of the subject. A)assumes B)assigns C)assures D)assembles 33. The specialist recommended that the exact nature of the woman's illness should be kept _____ her. A)from B)away from C)back from D)to 34. The introduction of fabrics made from rayon, nylon and other _____ fibers has made many changes in our civilization. A)magic B)arithmetic C)manufactured D)synthetic 35. Having decided to go abroad, he at once set _____ fulfilling his business in China. A)down B)in C)about D)apart 36. Even on week end, Mrs. Watson prefers doing something _____ doing nothing. A)than B)to C)rather than D)instead of 37. They were very disappointed _____ the findings of the Commission. A)from B)in C)on D)of 38. I ordered a lock in amplifier two weeks ago, and I think it is _____ that I will have it before next Saturday. A)possible B)probable
C)presumable D)likely 39. Having published his first novel earlier this year, he is starting in a new science fiction about traveling in space shuttle to the ma A)currently B)lately 40. Though badly damaged by fire, the most famous castle in this country was eventually to it s original splendid A)renewed B)repaired C)renovated D)restored Part Cloze Tes Directions: For each numbered blank in the following passage, there are four choices marked A, B, C, and D)Choose the best one and mark your answer on the aNSWER ShEeT by blackening the corresponding letter in the brackets. (10 It has been established beyond a shadow of doubt that readers in general waste a great deal of time and effort. Why is this so? Why is it that the poorest readers by whatever standard are often the ablest (41) people? Why is it that the majority of students have very little idea of how to tackle their reading? Why is it that a high (42)of readers not excluding those(43) professional work involves a lot of reading use a technique that is hardly more advanced than (44)they were children? Or why are there people to take an extreme but illuminating example who in conversation and discussion (45) sustain a difficult argument with ease and(46)Who as readers assimilate(u )only factual information, and (47) do that with difficulty, so that worthwhile books are virtually beyond them? In our opinion, reading(48)technical problems of communication that dispose the reader to use inappropriate methods of assimilation; this, and only (49), can provide an adequate explanation of why readers (50)a class are so ineffcient 41. A)of B)witl D)among B)I D)majority
C)presumable D)likely 39. Having published his first novel earlier this year, he is _____ starting in a new science fiction about traveling in space shuttle to the Mars. A)currently B)lately C)recently D)actually 40. Though badly damaged by fire, the most famous castle in this country was eventually _____ to it′s original splendor. A)renewed B)repaired C)renovated D)restored Part Ⅱ Cloze Test Directions: For each numbered blank in the following passage, there are four choices marked A,B,C, and D) Choose the best one and mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets.(10 points) It has been established beyond a shadow of doubt that readers in general waste a great deal of time and effort. Why is this so? Why is it that the poorest readers by whatever standard are often the ablest (41) people? Why is it that the majority of students have very little idea of how to tackle their reading? Why is it that a high (42) of readers not excluding those (43) professional work involves a lot of reading use a technique that is hardly more advanced than (44) they were children? Or why are there people to take an extreme but illuminating example who in conversation and discussion (45) sustain a difficult argument with ease and (46) Who as readers assimilate(吸 收) only factual information, and (47) do that with difficulty, so that worthwhile books are virtually beyond them? In our opinion, reading (48) technical problems of communication that dispose the reader to use inappropriate methods of assimilation; this, and only (49) , can provide an adequate explanation of why readers (50) a class are so ineffcient. 41. A)of B)with C)in D)among 42. A)rate B)percentage C)number D)majority 43. A)who B)whoever
C)who D)their B D)nevertheless 47. A)even even B)pr C)presents D)presents with B)this D)in this way B)like D)form PART I Reading Comprehension Each of the passages below is followed by some questions. For each question there are four answers marked A, B, C and D) Read the passages carefully and choose the best answer to each of the questions Then mark your answer on the aNSWEr SHEet by blackening the corresponding letter in the brackets(30 points
C)whose D)their 44. A)since B)as C)when D)that 45. A)would B)are going C)could D)will 46. A)so B)therefore C)not yet D)nevertheless 47. A)even B)even though C)such D)there is 48. A)presence B)present C)presents D)presents with 49. A)it B)this C)that D)in this way 50. A)as B)like C)in D)form PART Ⅲ Reading Comprehension Directions: Each of the passages below is followed by some questions. For each question there are four answers marked A,B,C and D) Read the passages carefully and choose the best answer to each of the questions. Then mark your answer on the ANSWER SHEET by blackening the corresponding letter in the brackets.(30 points) Passage 1
A vast health checkup is now being conducted in the western Swedish province of Varmland with the use of an automated apparatus for high speed multiple blood analyses. Deve loped by two brothers, the apparatu process more than 4, 000 blood samples a day, sub jecting each to 10 or more tests. Automation has cut the cost of the analyses by about 90 per cent The results so far have been astonishing, for hundreds of Swedes have learned that they have lent symptoms of disorders that neither they nor their physicians were aware of. Among them re iron deficiency anemia(3mf hE). high blood pressure, heart attack and even 尿病) The automated blood analysis apparatus was developed by dr. Gunnar Jungner, 49 year old associate professor of clinical chemistry at Goteborg University, and his brother, Ingmar 39, the physician in charge of the chemical central laboratory of Stockholms Hospital for Infectious Diseases. The idea was conceived 15 years ago when Dr. Gunnar Jungner was working as clinical chemist in northern Sweden and was asked by local physicians to devise a way of performing multiple analyses on a single blood sample. The design was ready in 1961. Consisting of calorimeters, pumps and other components, many of them American made, the Jungner apparatus was set up here in Stockholm. Samples from Varmland Province are drawn into the automated system at 90 second intervals. The findings clatter forth in the form of numbers printed by an automatic type writer. The Jungners predict that advance knowledge about a person's potential ailments(F) made possible by the chemical screening process will result in considerable savings in hospital and other medical costs. Thus, they point out, the blood analyses will actually turn out to cost nothing In the beginning, the automated blood analyses ran into considerable opposition from some physicians who had no faith in machines and saw no need for so many tests. Some laboratory technicians who saw their jobs threatened also protested. but the opposition is said to be warning. 51. The results of the use of the jungner apparatus indicate that a)person may become aware of an ailment not previously detected B)blood diseases can be cured very easily C)practically all Swedish physicians have welcomed the invention D)only one analysis may be made at a time 52. All of the following statements about automated blood analysis are true EXCEPt A)the analysis is recorded in a permanent form B)the idea for the apparatus involved an international effort C)the system has met opposition from physicians and technicians D)the machine is more efficient than other types of analysis 53. The main purpose of the passage is to A)predict the future of medical care B)describe a health checkup system C)warn about the dangers of undetected disease D)describe in detail the workings of a new machine
A vast health checkup is now being conducted in the western Swedish province of Varmland with the use of an automated apparatus for high speed multiple blood analyses. Developed by two brothers, the apparatus can process more than 4,000 blood samples a day, subjecting each to 10 or more tests. Automation has cut the cost of the analyses by about 90 per cent. The results so far have been astonishing, for hundreds of Swedes have learned that they have silent symptoms of disorders that neither they nor their physicians were aware of. Among them were iron deficiency anemia(贫血症).high blood pressure, heart attack and even diabetes(糖 尿病). The automeated blood analysis apparatus was developed by Dr.Gunnar Jungner, 49 year old associate professor of clinical chemistry at Goteborg University, and his brother, Ingmar, 39, the physician in charge of the chemical central laboratory of Stockholm′s Hospital for Infectious Diseases.The idea was conceived 15 years ago when Dr. Gunnar Jungner was working as clinical chemist in northern Sweden and was asked by local physicians to devise a way of performing multiple analyses on a single blood sample. The design was ready in 1961. Consisting of calorimeters, pumps and other components, many of them American made, the Jungner apparatus was set up here in Stockholm.Samples from Varmland Province are drawn into the automated system at 90 second intervals. The findings clatter forth in the form of numbers printed by an automatic type writer. The Jungners predict that advance knowledge about a person′s potential ailments(疾病) made possible by the chemical screening process will result in considerable savings in hospital and other medical costs. Thus, they point out, the blood analyses will actually turn out to cost nothing. In the beginning, the automated blood analyses ran into considerable opposition from some physicians who had no faith in machines and saw no need for so many tests. Some laboratory technicians who saw their jobs threatened also protested. But the opposition is said to be warning. 51. The results of the use of the jungner apparatus indicate that _____ . A)person may become aware of an ailment not previously detected B)blood diseases can be cured very easily C)practically all Swedish physicians have welcomed the invention D)only one analysis may be made at a time 52. All of the following statements about automated blood analysis are true EXCEPT: _____ . A)the analysis is recorded in a permanent form B)the idea for the apparatus involved an international effort C)the system has met opposition from physicians and technicians D)the machine is more efficient than other types of analysis 53. The main purpose of the passage is to _____ . A)predict the future of medical care B)describe a health checkup system C)warn about the dangers of undetected disease D)describe in detail the workings of a new machine
4. Automation is viewed by the writer with B)resentment vor D)indifference When, in the age of automation, man searches for a worker to do the tedious, unpleasant jobs that are impossible to mechanize, he may very profitably consider the ape. If we tackled the problem of breeding for brains with as much enthusiasm as we devote to breeding dogs of surrealistic shapes, we could eventually produce assorted(各式各样的) models of useful primates (k*e), ranging in size from the gorilla down to the little African monkey each adapted to a special kind of work. It is not putting too much strain on the imagination to assume that geneticists(遗传专家) could produce a super ape, able to understand some scores f words, and capable of being trained for such jobs as picking fruit, cleaning up the litter in parks, shining shoes, collecting garbage, doing household che baby sitting. Apes could do many jobs, such as cleaning streets and the more repetitive types of agricultural work, without supervision, though they might need protection from those nasty specimens of Homo sapiens who think it amusing to tease or bully anything they consider lower on the evolutionary ladder For other tasks, such as delivering papers and laboring on the dock our man ape would have to work under human overseers: and, incidentally, I would love to see the finale of the twenty first century version of On the Waterfront in which the honest but hairy hero will drum on his chest after literally taking the wicked labor leader apart. ce a supply of nonhuman workers becomes available, a whole range of low IQ jobs could be thankfully relinquished (f) by mankind, to its great mental and physical advantage What is more, one of the problems which has plagued so many fictional Utopias would be avoided there would be none of the degradingly(劣货的) subhuman Epsilons(智力低下的人) of Huxley’ s Brave New World to act as a permanent reproach(丢人现眼的人) to society, for there is a profound moral difference between breeding sub men and super apes, though the end products are much the same The first would introduce a form of slavery; the second would be a biological triumph which could nefit both men and animals 55. Until now, man has enthusiastically tackled the problems of A)breeding for brains B)breeding dogs of surrealistic shapes C)producing intelligent gorillas D)producing useful primates 56. In the author s opinion, the idea that geneticists could produce a super ape i A)a strain on the imagination B)demonstrably tr C) plausib1(似合理的 D)biologically impossible
54. Automation is viewed by the writer with _____ . A)indecision B)resentment C)favor D)indifference Passage 2 When, in the age of automation, man searches for a worker to do the tedious, unpleasant jobs that are impossible to mechanize, he may very profitably consider the ape. If we tackled the problem of breeding for brains with as much enthusiasm as we devote to breeding dogs of surrealistic shapes, we could eventually produce assorted(各式各样的) models of useful primates (灵长类), ranging in size from the gorilla down to the little African monkey, each adapted to a special kind of work. It is not putting too much strain on the imagination to assume that geneticists(遗传专家) could produce a super ape, able to understand some scores of words, and capable of being trained for such jobs as picking fruit, cleaning up the litter in parks, shining shoes, collecting garbage, doing household chores, and even baby sitting. Apes could do many jobs, such as cleaning streets and the more repetitive types of agricultural work, without supervision, though they might need protection from those nasty specimens of Homo sapiens who think it amusing to tease or bully anything they consider lower on the evolutionary ladder. For other tasks, such as delivering papers and laboring on the docks, our man ape would have to work under human overseers; and, incidentally, I would love to see the finale of the twenty first century version of On the Waterfront in which the honest but hairy hero will drum on his chest after literally taking the wicked labor leader apart. Once a supply of nonhuman workers becomes available, a whole range of low IQ jobs could be thankfully relinquished(放弃) by mankind, to its great mental and physical advantage. What is more, one of the problems which has plagued so many fictional Utopias would be avoided. There would be none of the degradingly (劣货的) subhuman Epsilons(智力低下的人) of Huxley′s Brave New World to act as a permanent reproach(丢人现眼的人) to society, for there is a profound moral difference between breeding sub men and super apes, though the end products are much the same. The first would introduce a form of slavery; the second would be a biological triumph which could benefit both men and animals. 55. Until now, man has enthusiastically tackled the problems of _____ . A)breeding for brains B)breeding dogs of surrealistic shapes C)producing intelligent gorillas D)producing useful primates 56. In the author′s opinion, the idea that geneticists could produce a super ape is _____ . A)a strain on the imagination B)demonstrably true C)plausibl(似合理的) D)biologically impossible
57. The author states that a supply of nonhuman workers for low IQ jobs world A)upset the nation' B)benefit man mentally and physically C)be a disadvantage to many human workers D)enrage the Society for Prevention of Cruelty to Animals 58. The author of this article i B)revealing his low opinion of mankind C)expressing his doubts about the possibility of breeding a super ape D)presenting a plausible theory in a humorous tone 3 The atmosphere is a mixture of several gases. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere under all natural conditions. of these permanent gases, oxygen makes up about 2l per cent and nitrogen about 78 per cent. Several other gases, such as argon, carbon dioxide, hydrogen, neon, krypton, and one per cent of the volume of dry air. The amount of water vapor, and its variations in amount and distribution is of extraordinary importance in weather changes. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke, and other impurities which are always present in considerable. but variable amounts. The atmosphere has no definite upper limits but gradually thins untill it becomes imperceptible(难以察觉的). Until recently it was assumed that the air above the first few miles gradually grew thiner and colder at a constant rate. It was also assumed that upper air had little influence on weather changes. Recent studies of the upper atmosphere, currently being conducted by earth satellites and missile probings ( T), have shown these assumptions to be incorrect. he atmosphere has three well defined strata(z) The layer of the air next to the earth, which extends upward for about ten miles, is known as the troposphere(xf iti E). On the whole, it makes up about 75 per cent of all the weight of the atmosphere. It is the warmest part of the atmosphre because most of the solar radiation is absorbed by the earth s surface which warms the air immediately surrounding it. A steady decrease o temperature with increasing elevation is a most striking characteristic. The upper layers are colder because of their greater distance from the earth s surface and rapid radiation of heat into space. The temperatures within the troposphere decrease about 3.5 degrees per 1, 000 feet increase in altitude. Within the troposphere, winds and air currents distribute heat and moisture Strong winds called jet streams, are located at the upper levels of the troposphe streams are both complex and widespread in occurrence. They normally show a wave shaped patter and move from west to east at velocities of 150 mph, but velocities as high as 400 mph have been noted. The influences of changing locations and strengths of jet streams upon weather conditions and patterns are no doubt considerable. Current intensive research may eventually reveal their true significance Above the troposphere to a height of about 50 miles is a zone called the stratosphere(f im 2). The stratosphere is separated from the troposphere by a zone of uniform temperatures called the tropopause. Within the lower portion of the stratosphere is a layer of ozone(5 0)gases which
57. The author states that a supply of nonhuman workers for low IQ jobs world _____ . A)upset the nation′s economy B)benefit man mentally and physically C)be a disadvantage to many human workers D)enrage the Society for Prevention of Cruelty to Animals 58. The author of this article is _____ . A)merely attempting to be humorous B)revealing his low opinion of mankind C)expressing his doubts about the possibility of breeding a super ape D)presenting a plausible theory in a humorous tone Passage 3 The atmosphere is a mixture of several gases. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere under all natural conditions. of these permanent gases, oxygen makes up about 21 per cent and nitrogen about 78 per cent. Several other gases, such as argon, carbon dioxide, hydrogen, neon, krypton, and xenon, comprise the remaining one per cent of the volume of dry air. The amount of water vapor, and its variations in amount and distribution is of extraordinary importance in weather changes. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke, and other impurities which are always present in considerable, but variable amounts. The atmosphere has no definite upper limits but gradually thins untill it becomes imperceptible(难以察觉的). Until recently it was assumed that the air above the first few miles gradually grew thiner and colder at a constant rate. It was also assumed that upper air had little influence on weather changes. Recent studies of the upper atmosphere, currently being conducted by earth satellites and missile probings(探查), have shown these assumptions to be incorrect. The atmosphere has three well defined strata(层). The layer of the air next to the earth, which extends upward for about ten miles, is known as the troposphere(对流层).On the whole, it makes up about 75 per cent of all the weight of the atmosphere. It is the warmest part of the atmosphre because most of the solar radiation is absorbed by the earth's surface which warms the air immediately surrounding it. A steady decrease of temperature with increasing elevation is a most striking characteristic. The upper layers are colder because of their greater distance from the earth's surface and rapid radiation of heat into space. The temperatures within the troposphere decrease about 3.5 degrees per 1,000 feet increase in altitude. Within the troposphere, winds and air currents distribute heat and moisture. Strong winds called jet streams, are located at the upper levels of the troposphere. These jet streams are both complex and widespread in occurrence. They normally show a wave shaped pattern and move from west to east at velocities of 150 mph, but velocities as high as 400 mph have been noted. The influences of changing locations and strengths of jet streams upon weather conditions and patterns are no doubt considerable. Current intensive research may eventually reveal their true significance. Above the troposphere to a height of about 50 miles is a zone called the stratosphere(同 温层).The stratosphere is separated from the troposphere by a zone of uniform temperatures called the tropopause. Within the lower portion of the stratosphere is a layer of ozone(臭氧) gases which