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发布时间：2006-06-21 20:59     点击：

(D) general perception that iron structures were not aesthetically pleasing

22. The paragraph following the passage most probably discusses

(A) the gradual inclusion of exposed iron in traditional styles of architecture

(B) further improvements in iron processing methods

(C) the return to traditional building materials for use in commercial structures

(D) the decreased use of stone and timber as a building material

Questions 23——32

The most easily recognizable meteorites are the iron variety, although they only represent about 5 percent of all meteorite falls. They are composed of iron and nickel along with sulfur, carbon, and traces of other elements. Their composition is thought to he similar to that of Earth's iron core 3 and indeed they might have once made up the core of a large planetoid that disintegrated long ago. Due to their dense structure, iron meteorites have the best chance of surviving an impact, and most are found by farmers plowing their fields.

One of the best hunting grounds for meteorites is on the glaciers of Antarctica1 where the dark stones stand out in stark contrast to the white snow and ice. When

meteorites fall on the continent) they are embedded in the moving ice sheets. At places where the glaciers move upward against mountain ranges, meteorites are left exposed on the surface. Some of the meteorites that have landed in Antarctica are believed to have conic from the Moon and even as far away as Mars, when large impacts blasted out chunks of material and hurled them toward Earth.

Stony meteorites, called chordates, are the most common type and make up more than 90 percent of all falls . But because they are similar to Earth materials and therefore erode easily, they are often difficult to find. Among the most ancient bodies in the solar system are the carbonaceous chondrites that also contain carbon compounds that might have been the precursors of life on Earth.

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