求助~OG12 117题

jessicaliuruc

文章在OG PAGE400

117.The authors’ suggestion that “as much as 90 percent
of the mass of the universe is not radiating at any
wavelength with enough intensity to be detected on
the Earth” (lines 34–37) would be most weakened if
which of the following were discovered to be true?
(A) Spiral galaxies are less common than types of
galaxies that contain little nonluminous matter.
(B) Luminous and nonluminous matter are
composed of the same basic elements.
(C) The bright nucleus of a typical spiral galaxy also
contains some nonluminous matter.
(D) The density of the observable universe is
greater than most previous estimates have
suggested.
(E) Some galaxies do not rotate or rotate too slowly

哪位高人帮忙解答一下~~看了解答，我理解Spiral galaxies 不是普遍现象，就不能推出后面结论的解释~~但是我不太明白，答案里面为什么要把 Spiral galaxies 与
galaxies that contain little nonlumious matter 来做比较呢？~~

默默楚

我也不明白 同问！牛牛快来解答呀~

fkendia

我也正犯愁呢！不过我大概试着自己勉强理解了一下，欢迎各路板砖！

首先，一般这种定位题是要结合上下文看的，尤其看相近的前后两句话。这一题主要是看前一句，因为题干句里面的mass指代的是前一句里的nonluminous mass，而 luminous mass可以被increase in nonluminous mass平衡掉，也就是说不发光质量增多导致了发光质量减少。

第二，第二段里面提到it has been know for some time that outside the bright nucleus of a typical spiral galaxy luminosity falls off rapidly with distance from the center（已知一段时间在一个典型的旋涡星系的发光核体外部，亮度随着离中心的距离越来越远而大幅下降），后面又说Outside the nucleus the rotational velocity would decrease geometrically with distance from the center，（在核体外部自转速度应该随着离中心的地理距离越来越远而下降），但是Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly（反之，我们却发现漩涡星系的自转速度随着距离的增加而保持稳定或轻微增长）。结合题干句的前一句，This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.（这个出乎意料的结果表明发光质量随距离中心的减少是被不发光质量的增加而平衡掉的）。

先是说这些universe星体都是存在于typical spiral galaxies这个典型的漩涡星系里面的，星系是星体的载体；然后，典型漩涡星系是包含多的不发光质量，那非典型旋涡星系就应该是包含少的不发光质量；最后，如果他们用的例子是非典型的，则题干被削弱，也就是说一个典型的例子不足以说明问题。

sissiyu

fkendia 发表于 2012-12-10 00:56
我也正犯愁呢！不过我大概试着自己勉强理解了一下，欢迎各路板砖！首先，一般这种定位题是要结合上下文看的 ...

最后是不是应该是非典型的例子不足以证明由此而做出的结论呢？