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2010年6月20日大学英语四级考试冲刺模拟卷(5)

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Part V Cloze (15 minutes)

Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A), B), C) and D) on the right side of the paper. You should choose the ONE that best fits into the passage. Then mark the corresponding letter on Answer Sheet 2 with a single line through the centre.

Ever since the Mayflower dropped anchor in 1620, American settlers have migrated west, clearing the land of trees to make way for farms, homes and factories. Since then, nearly all the forests of the Eastern United States have been chopped 67 at one time or another.

Why, then, of the approximately 160 kinds of birds that 68 the area from the Atlantic coast to the central plains and from Maine 69 Florida, have only four 70? That constitutes a rate of extinction far 71 what ecologists might expect from such a 72 loss of habitat. Critics have used the 73 low number to challenge conservationists' 74 that widespread deforestation in some parts of the world will 75 lead to a severe loss in biodiversity.

In an article being 76 today in The Proceedings of the National Academy of Sciences, Dr. Stuart L. Pimm and Dr. Robert A. Askins examine the history of 77 in the East and subsequent extinctions of bird species. Dr. Pimm, an ecologist at the University of Tennessee in Knoxville, argues that 78 endemic species -- those which live in the Eastern United States forests and 79 else -- are counted, the calculations of expected species loss hold 80.

One reason, he says, is that the Eastern forest was never cut all at once; 81 the woodlands of Ohio were being felled by farmers moving 82, for example, those cut earlier in New England were regenerating. 83, there were always enough refuges for most forest birds.

But other biologists say that even with the revised counting method, forecasting extinction rates is an 84 art.

The theory used to estimate species loss predicts that as an area of habitat is 85, species will disappear at a predictable rate. If a habitat 86 by half, for example, the theory predicts a 15 percent loss of species; a reduction of 90 percent of a given habitat would eventually cause half the species to disappear.

67. A) down B) up C) on D) in

68. A) lived B) supported C) inhabited D) evolved

69. A) down B) to C) with D) up

70. A) raised B) added C) revived D) vanished

71. A) many B) far C) less D) vast

72. A) above B) almost C) below D) under

73. A) strikingly B) obviously C) sharply D) differently

74 A) words B) claims C)estimates D) displays

75. A)increasingly B) exclusively C) inevitably D) exceedingly

76. A) predicted B) worked C) proved D) published

77. A) planting B) forestation C) deforestation D) cultivation

78. A) Hence B) unless C) if only D)only if

79. A) nowhere B) everywhere C) anywhere D) place

80. A) down B) up C) in D) on

81. A) when B) once C) while D) whereas

82. A) west B) east C) north D) south

83. A) In case B) Though C) while D) Thus

84. A) imprecise B) precise C) proper D) improper

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