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  3. The space between the stars is filled with matter that interstellar conditions should prevent from coalescing into solid particl

The space between the stars is filled with matter that interstellar conditions should prevent from coalescing into solid particl

admin2020-03-28  90
问题     The space between the stars is filled with matter that interstellar conditions should prevent from coalescing into solid particle. Yet surprisingly tiny frozen particles, referred to as interstellar grains, do develop in these spaces. These grains are formed out of chemical elements that are synthesized during thermonuclear fusion in stars and supernova explosions.
    The study of interstellar grains has been hampered by the inaccessibility of naturally occurring specimens for use in laboratory experiments. To date, the only source of information about interstellar grains is the stellar electromagnetic radiation that reaches the Earth after passing through regions of space containing interstellar grains. By observing the wavelengths scattered and absorbed by the grains scientists have determined that a grain’s internal structure consists of a core composed of silicates (rocklike material) and a mantle composed entirely of organic compounds. It is hypothesized that each grain begins as a silicate “seedling” ejected from a mature star. Continuous physical and chemical evolution then occurs in the mantle formed around the seedling.
It can be inferred from the passage that the method currently used to analyze the structure of an interstellar grain could best be described is
选项 A、Unprecedented
B、Indirect
C、Comprehensive
D、Controversial
E、Unsound
答案B
解析 根据第二段第一句可知，因为没法得到星际颗粒的标本，因此星际颗粒的研究方法都是间接的，选项B正确。
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本试题收录于： GRE VERBAL题库GRE分类
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