新GRE逻辑阅读 每日一练25

　　编辑点评： GRE阅读考试的材料，非常强调逻辑的关系，所以逻辑要点是大家在解GRE阅读题的时候的关键，本文就为大家例举了这样一篇逻辑短文，供大家参考和练习。

　　随着GRE阅读考试的难度日益增加，大家需要有针对性地进行练习，本文为大家例举的就是逻辑短文的练习，文末还附有答案，供大家更好地练习。

　　If a supernova trig-gered star formation from dense clouds of gas and dust, and if the most massive star to be formed from the cloud evolved into a supernova and triggered a new round of star formation, and so on, then a chain of star-forming regions would result. If many such chains were created in a differentially rotating galaxy, the distribution of stars would resemble the observed distribute in a spiral galaxy.

　　This line of reasoning underlies an exciting new theory of spiral-galaxy structure. A computer simulation based on this theory has reproduced the appearance of many spiral galaxies without assuming an underlying density wave, the hallmark of the most widely accepted theory of the large-scale structure of spiral galaxies.That theory maintains that a density wave of spiral form sweeps through the central plane of a galaxy, compressing clouds of gas and dust, which collapse into stars that form a spiral pattern.

　　7. The primary purpose of the passage is to

　　describe what results when a supernova triggers the creation of chains of star-forming regions

　　propose a modification in the most widely accepted theory of spiral-galaxy structure

　　compare and contrast the roles of clouds of gas and dust in two theories of spiral-galaxy structure

　　describe a new theory of spiral-galaxy structure and contrast it with the most widely accepted theory

　　describe a new theory of spiral-galaxy structure and discuss a reason why it is inferior to the most widely accepted theory

　　8. The passage implies that, according to the new theory of spiral-galaxy structure, a spiral galaxy can be created by supernovas when the supernovas are

　　producing an underlying density wave

　　affected by a density wave of spiral form

　　distributed in a spiral pattern

　　located in the central plane of a galaxy

　　located in a differentially rotating galaxy

　　9. Which of the following, if true, would most discredit the new theory as described in the passage?

　　The exact mechanism by which a star becomes a supernova is not yet completely known and may even differ for different stars.

　　Chains of star-forming regions like those postulated in the new theory have been observed in the vicinity of dense clouds of gas and dust.

　　The most massive stars formed from supernova explosions are unlikely to evolve into super-novas.

　　Computer simulations of supernovas provide a poor picture of what occurs just before a supernova explosion.

　　A density wave cannot compress clouds of gas and dust to a density high enough to create a star.

　　答案：D/E/C

　　上文的题目大家答对了几题?大家不仅要多做题，更要善于总结，这样才会有针对性地提高。