逻辑晕菜题3

本题是page 37  chenxiangdong No.8

It has been hypothesized that much of the matter in the universe is “dark”, i.e, unseen. Studies have shown that galaxies in many galaxy clusters are moving faster with respect to one another than they would if visible stars constituted all their mass. The studies suggest that the galaxies are moving under the gravitational influence of unseen mass in considerable quantity.

C)     the aggregate mass of visible stars in the galaxies mentioned above can be estimated with some confidence.

D)     without exception, the galaxies mentioned above move toward one another

本题的正确答案是C，可是自由当时选的是D，请大家指点一下，自由的D为什么错啊？谢谢大家。

assumption题（自由可能忘了帖问题了吧)

move toward 我的理解是相对运动，可文中只提到move相对的快慢(faster),没有提到方向问题，所以不对。

A. Measurements of the speed of moving galaxies are extremely unreliable.

B. The workings of gravitational forces are not particularly well understood.

C the aggregate mass of visible stars in the galaxies mentioned above can be estimated with some confidence.

D the general composition of unseen matter in the universe has been determined.

E  without exception, the galaxies mentioned above move toward one another

E, without exception, the galaxies mentioned above move toward one another取反，也就是the galaxies mentioned above 彼此相反运动或是在空中没有规律的乱动只要不相向，这并不影响或是说并不能否定结论 galaxies are moving under the gravitational influence of unseen mass in considerable quantity. 我认为这是无关的。

C取反， the aggregate mass of visible stars in the galaxies mentioned above 不能 be estimated ，也就是有些visible stars 是未被知道的，这样研究所展现出的现象 galaxies in many galaxy clusters are moving faster with respect to one another than they would if visible stars constituted all their mass.不一定得出结论或是说被结论 galaxies are moving under the gravitational influence of unseen mass in considerable quantity所解释，因为这种现象有可能是未知的mass of visible stars 所引起的。所以C是个assumption。

我做题没用ZXD的方法，所以无法清晰地从他做题的思路入手对这题进行分析。我上面的取反推论也不一定对，不过是我做题时的想法，只能参考一下。另外我认为C是个相关项，因为天体速度的快慢跟它本身及宇宙中其它天体的质量是紧密相关的。

非常感谢楼上各位朋友的帮助,特别是7楼朋友的宝贵帮助. 其实7楼朋友,您的思维方式,也是一种很重要的逻辑思维方式, 就是新东芳对于逻辑难题的答案选项的否定筛选, 自由反复琢磨了这个题目, 觉得这个题目其实比较难, 也许自由GMAT水平不高的缘故吧, 可能许多牛牛们认为这个题目并不难.我觉得E这个选项真的比较容易误选.因为自由感觉C好象是题干第一句话的同义变换. 题目本身就是问这个"推论"的假设是什么,那么就干脆对题干第一句话进行同义变换就可以了. 另外,自由觉得,这个题干出现最多的字眼就是unseen mass, seen mass质量这个频率很高的字眼. 所以选C?  不过E感觉真的也是很有道理的假设,因为只有物体之间的相互运动的存在性,才可能推论出宇宙物体之间运动速度快慢问题,从而得出了可见的物质多,还是不可见的物质多. 自由考虑到现在,还是对这个题目心存疑惑, 希望各位朋友有时间给自由更多的建议,让有限的思路扩展无限.谢谢大家.