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1、精品文档0308 托福试题阅读( 55minutes)Question 1-11If food is allowed to stand for some time, it putrefies .When the putrefied materialis examined microscopically ,it is found to be teeming with bacteria. Where do thesebacteria come from , since they are not seen in fresh food? Even until the mid-nineteenthcen
2、tury, many people believed that such microorganisms originated by spontaneous(5 ) generation ,a hypothetical process by which living organisms develop from nonlivingmatter.The most powerful opponent of the theory of spontaneous generation was the French chemist and microbiologist Louis Pasteur(1822-
3、1895).Pasteur showed that structures present in air closely resemble the microorganisms seen in putrefying materials .He did(10) this by passing air through guncotton filters, the fibers of which stop solid particles. Afterthe guncotton was dissolved in a mixture of alcohol and ether, the particles
4、that it hadtrapped fell to the bottom of the liquid and were examined on a microscope slide .Pasteurfound that in ordinary air these exists a variety of solid structures ranging in size from0.01 mm to more than 1.0 mm .Many of these bodies resembled the reproductive(15)structures of common molds, si
5、ngle-celled animals, and various other microbial cells .As many as 20 to 30 of them were found in fifteen liters of ordinary air ,and they couldnot be distinguished from the organisms found in much larger numbers in putrefying materials .Pasteur concluded that the organisms found in putrefying mater
6、ials originatedfrom the organized bodies present in the air .He postulated that精品文档these bodies are constantly(20)being deposited on all objects.Pasteur showed that if a nutrient solution was sealed in a glass flask and heated toboiling to destroy all the living organisms contaminating it, it never
7、putrefied .The proponents of spontaneous generation declared that fresh air was necessary for spontaneous generation and that the air inside the sealed flask was affected in some way(25)by heating so that it would no longer support spontaneous generation. Pasteur constructed a swan-necked flask in w
8、hich putrefying materials could he heated to boiling, but air could reenter. The bends in the neck prevented microorganisms from getting in the flask. Material sterilized in such a flask did not putrefy.1, What does the passage mainly discuss?(a) Pasteur s influence on the development of the microsc
9、ope.(b) The origin of the theory of spontaneous generation .(c) The effects of pasteurization on food.(d) Pasteur s argumentnasgt athi e theory of spontaneous generation .2, The phrase “ teeming with” in line 2 is closest in meaning to(a) full of(b) developing into(c) resistant to(d) hurt by3, Which
10、 of the following questions did the theory of spontaneous generation attempt to answer?(a) What is the origin of the living organisms are seen on some food?(b) How many types of organisms can be found on food?(c) What is the most effective way to prepare living organisms for microscopic examination?
11、(d) How long can food stand before it putrefies?4, The word “ resemble ” in line 9 is closest in meaning to(a) benefit from(b) appear similar to(c) join together with(d) grow from5, The purpose of the“ guncotton ” mentioned in paragraph 2 was to(a) trap particles for analysis(b) slow the process of
12、putrefaction(c) increase the airflow to the microscopic slide(d) aid the mixing of alcohol and ether6, The author mention“ 1.0mm” in line 14 in describing the(a) thickness of a layer of organisms that was deposited on an object(b) diameter of the fibers that were in the guncotton filters(c) thicknes
13、s of the microscope slides that were used(d) size of the particles that that were collected7. The word “ postulated ”in line 19 is closest in meaning to(a) analyzed(b) doubted(c) persuaded(d) suggested8. The objects that Pasteut removed from the air in his experiment were remarkable because they wer
14、e(a) primarily single-celled organisms(b) no different from objects found in putrefying materials(c) fairly rare(d) able to live in a mixture of alcohol and ether9. The word “ it ” in line 22 refers to(a) a nutrient solution(b) a glass flask(c) boiling(d) spontaneous generation10. According to parag
15、raph 3,proponents of spontaneous generation believed that which of the following was important for the process to succeed ?(a) A sealed container(b) Fresh air(c) Heat(d) The presence of nutrients11.It can be inferred from paragraph 3 that Pasteur employed a swam-necked flask to(a) store sterilized l
16、iquids for use in future experiments(b) prevent heat from building up in a solution(c) disprove a criticism of his conclusions(d) estimate the number of organisms in a liter of airQuestions 12-20In the early decades of the United States ,the agrarian movement promoted the farmeras society hsero. In the minds of agrarian
