Reading Comprehension
试题详情
文章：
After evidence was obtained in the 1920s that the universe is expanding, it became reasonable to ask: Will the universe continue to expand indefinitely, or is there enough mass in it for the mutual attraction of its constituents to bring this expansion to a halt? It can be calculated that the critical density of matter needed to brake the expansion and "close" the universe is equivalent to three hydrogen atoms per cubic meter. But the density of the observable universe-luminous matter in the form of galaxies-comes to only a fraction of this. If the expansion of the universe is to stop, there must be enough invisible matter in the universe to exceed the luminous matter in density by a factor of roughly 70.
Our contribution to the search for this "missing matter" has been to study the rotational velocity of galaxies at various distances from their center of rotation. It has been known for some time that outside the bright nucleus of a typical spiral galaxy luminosity falls off rapidly with distance from the center. If luminosity were a true indicator of mass, most of the mass would be concentrated toward the center. Outside the nucleus the rotational velocity would decrease geometrically with distance from the center, in conformity with Kepler's law. Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly. This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.
Our findings suggest 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. Such dark matter could be in the form of extremely dim stars of low mass, of large planets like Jupiter, or of black holes, either small or massive. While it has not yet been determined whether this mass is sufficient to close the universe, some physicists consider it significant that estimates are converging on the critical value.
Our contribution to the search for this "missing matter" has been to study the rotational velocity of galaxies at various distances from their center of rotation. It has been known for some time that outside the bright nucleus of a typical spiral galaxy luminosity falls off rapidly with distance from the center. If luminosity were a true indicator of mass, most of the mass would be concentrated toward the center. Outside the nucleus the rotational velocity would decrease geometrically with distance from the center, in conformity with Kepler's law. Instead we have found that the rotational velocity in spiral galaxies either remains constant with increasing distance from the center or increases slightly. This unexpected result indicates that the falloff in luminous mass with distance from the center is balanced by an increase in nonluminous mass.
Our findings suggest 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. Such dark matter could be in the form of extremely dim stars of low mass, of large planets like Jupiter, or of black holes, either small or massive. While it has not yet been determined whether this mass is sufficient to close the universe, some physicists consider it significant that estimates are converging on the critical value.
题目：
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" (highlight text) would be most weakened if which of the following were discovered to be true?
选项:
A、Spiral galaxies are less common than types of galaxies that contain little nonluminous matter.Luminous and nonluminous matter are composed of the same basic elements.
B、The bright nucleus of a typical spiral galaxy also contains some nonluminous matter.
C、The density of the observable universe is greater than most previous estimates have suggested.
D、Some galaxies do not rotate or rotate too slowly for their rotational velocity to be measured.
答案:
A
提问：
这个题目想要请英吉老师回答一下，我是之前广州班的学生，这个题目想要请老师来解答一下,这个题目我选的The density of the observable universe is greater than most previous estimates have suggested.选什么不重要重要的是思路就不对定位就定错了，我一看到这道削弱题我就往高亮处这句话的下面去找了（我觉得是第二段和第三段段间关系没有理清导致的），然后找来找去也没找到，看到正确答案也不知道这个正确答案是怎么来的，希望老师可以解答一下！
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提问：
What is the value of the two-digit number X
1 The sum if the two digits is 4
2 The difference between the two digits is 2
这道题问的是两位数X的值是多少，题干中并没有说X是唯一值
根据两个条件很容易算出X的两个值，
两个条件都是有用的，而且题干所给信息并未说X具有唯一性
为什么答案是E，而不是C？
是不是Data Sufficiency要得出的必须是唯一值，不可以是两个值
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