GMAT考试阅读辅导（12）.

　　Passage 12

　　Nearly a century ago, biologists found that if they separated an invertebrate animal embryo into two parts at an early stage of its life, it would survive and develop as two normal embryos. This led them to believe that the (5)?cells in the early embryo are undetermined in the sense that each cell has the potential to develop in a variety of different ways. Later biologists found that the situation was not so simple. It matters in which plane the embryo is cut. If it is cut in a plane different from the one used (10) by the early investigators, it will not form two whole embryos.

　　A debate arose over what exactly was happening. Which embryo cells are determined, just when do they- become irreversibly committed to their fates, and what (15) are the “morphogenetic determinants” that tell a cell Passage 15

　　In the two decades between 1910 and 1930, over ten percent to the Black population of the United States lt the South, where the preponderance of the Black population had been located, and migrated to northern (5) states, with the largest number moving, it is claimed, between 1916 and 1918. It has been frequently assumed, but not proved, that the majority of the migrants in what has come to be called the Great Migration came from rural areas and were motivated by two concurrent (10factors: the collapse of the cotton industry following the boll weevil infestation, which began in 1898, and increased demand in the North for labor following the cessation of European immigration caused by the outbreak of the First World War in 1914. his assump- (15) tion has led to the conclusion that the migrants’ subsequent lack of economic mobility in the North is tied to rural background, a background that implies unfamiliarity with urban living and a lack of industrial skills.

　　But the question of who actually lt the South has (20) never been rigorously investigated. Although numerous investigations document an exodus from rural southern areas to southern cities prior to the Great Migration. no one has considered whether the same migrants then moved on to northern cities. In 1910 over 600,000 (25) Black workers, or ten percent of the Black work force, reported themselves to be engaged in “manufacturing and mechanical pursuits,” the federal census category roughly encompassing the entire industrial sector. The Great Migration could easily have been made up entirely (30) of this group and their families. It is perhaps surprising to argue that an employed population could be enticed to move, but an explanation lies in the labor conditions then prevalent in the South. About thirty-five percent of the urban Black popu-(35) lation in the South was engaged in skilled trades. Some were from the old artisan class of slavery-blacksmiths. masons, carpenters-which had had a monopoly of certain trades, but they were gradually being pushed out by competition, mechanization, and obsolescence, (40) The remaining sixty-five percent, more recently urbanized, worked in newly developed industries---tobacco. lumber, coal and iron manufacture, and railroads. Wages in the South, however, were low, and Black workers were aware, through labor recruiters and the (45)Black press, that they could earn more even as unskilled workers in the North than they could as artisans in the South. After the boll weevil infestation, urban Black workers faced competition from the continuing influx of both Black and White rural workers, who were driven (50) to undercut the wages formerly paid for industrial jobs. Thus, a move north would be seen as advantageous to a group that was already urbanized and steadily employed, and the easy conclusion tying their subsequent economic problems in the North to their rural background comes into question.

　　1. The author indicates explicitly that which of the following records has been a source of information in her investigation?

　　?(A) United States Immigration Service reports from 1914 to 1930

　　?(B) Payrolls of southern manufacturing firms between 1910 and 1930

　　?(C) The volume of cotton exports between 1898 and 1910

　　?(D) The federal census of 1910

　　?(E) Advertisements of labor recruiters appearing in southern newspapers after 1910

　　2. In the passage, the author anticipates which of the following as a possible objection to her argument?

　　?(A) It is uncertain how many people actually migrated during the Great Migration.

　　?(B) The eventual economic status of the Great Migration migrants has not been adequately traced.

　　?(C) It is not likely that people with steady jobs would have reason to move to another area of the country.

　　?(D) It is not true that the term “manufacturing and mechanical pursuits” actually encompasses the entire industrial sector.

　　?(E) Of the Black workers living in southern cities, only those in a small number of trades were threatened by obsolescence.

　　3. According to the passage, which of the following is true of wages in southern cities in 1910?

　　?(A) They were being pushed lower as a result of increased competition.

　　?(B) They had begun t to rise so that southern industry could attract rural workers.

　　?(C) They had increased for skilled workers but decreased for unskilled workers.

　　?(D) They had increased in large southern cities but decreased in small southern cities.

　　?(E) They had increased in newly developed industries but decreased in the older trades.

　　4. The author cites each of the following as possible influences in a Black worker’s decision to migrate north in the Great Migration EXCEPT

　　?(A) wage levels in northern cities

　　?(B) labor recruiters

　　?(C) competition from rural workers

　　?(D) voting rights in northern states

　　?(E) the Black press

　　5. It can be inferred from the passage that the “easy conclusion” mentioned in line 53 is based on which of the following assumptions?

　　?(A) People who migrate from rural areas to large cities usually do so for economic reasons.

　　?(B) Most people who leave rural areas to take jobs in cities return to rural areas as soon as it is financially possible for them to do so.

　　?(C) People with rural backgrounds are less likely to succeed economically in cities than are those with urban backgrounds.

　　?(D) Most people who were once skilled workers are not willing to work as unskilled workers.

　　?(E) People who migrate from their birthplaces to other regions of country seldom undertake a second migration.

　　6. The primary purpose of the passage is to

　　?(A) support an alternative to an accepted methodology

　　?(B) present evidence that resolves a contradiction

　　?(C) introduce a recently discovered source of information

　　?(D) challenge a widely accepted explanation

　　?(E) argue that a discarded theory deserves new attention

　　7. According to information in the passage, which of the following is a correct sequence of groups of workers, from highest paid to lowest paid, in the period between 1910 and 1930?

　　?(A) Artisans in the North; artisans in the South; unskilled workers in the North; unskilled workers in the South

　　?(B) Artisans in the North and South; unskilled workers in the North; unskilled workers in the South

　　?(C) Artisans in the North; unskilled workers in the North; artisans in the South

　　?(D) Artisans in the North and South; unskilled urban workers in the North; unskilled rural workers in the South

　　?(E) Artisans in the North and South, unskilled rural workers in the North and South; unskilled urban workers in the North and South

　　8. The material in the passage would be most relevant to a long discussion of which of the following topics?

　　?(A) The reasons for the subsequent economic difficulties of those who participated in the Great Migration

　　?(B) The fect of migration on the regional economies of the United States following the First World War

　　?(C) The transition from a rural to an urban existence for those who migrated in the Great Migration

　　?(D) The transformation of the agricultural South following the boll weevil infestation

　　?(E) The disappearance of the artisan class in the United States as a consequence of mechanization in theearly twentieth century