附阅读： In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers.Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larger. Because these galaxies’ mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars—that is, they evolve much more slowly. GWD-4-Q37:
It can be inferred from the passage that which of the following is an accurate physical description of typical low-surface-brightness galaxies?
A.They are large spiral galaxies containing fewer stars than do conventional galaxies.
B.They are compact but very dim spiral galaxies.
C.They are diffuse spiral galaxies that occupy a large volume of space.
D.They are small, young spiral galaxies that contain a high proportion of primordial gas.
E.They are large, dense spirals with low luminosity.
为什么不选A呢？原文说了 1.these galaxiestend to be much larger 2.they have far fewer stars per unit volume than do conventional galaxies，C 选项 中的diffuse 从哪里能看出呢？还有 spiral 哪里有信息说它是可以旋转的啊？ 求教！！！
因为这些星系其实have the same general shape and even the same approximate number of stars 而且注意far fewer stars后面还有 per unit volume~ 所以containing fewer stars 的表述是不对的~
BE都错在说dim galaxies（low-surface-bringhtness）是紧凑的，但是从文中可以看出这个星系是松散的，所以平均每个空间量度星星的数量比常规星系少。具体来自这句话——Because these galaxies’ mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies.
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发表于 2011-8-8 18:08:57
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