GWD27-Q10 to Q12

Astronomers theorize that a black

      hole forms when a massive object

      shrinks catastrophically under its own

Line gravity, leaving only a gravitational

  (5)field so strong that nothing escapes it.

Astronomers must infer the existence

of black holes, which are invisible,

from their gravitational influence on

the visible bodies surrounding them.

 (10)For example, observations indicate

that gas clouds in galaxy M87 are

whirling unusually fast about the gal-

axy’s center.  Most astronomers

believe that the large concentration

 (15)of mass at the galaxy’s center is a

black hole whose gravity is causing

the gas to whirl.  A few skeptics have

argued that the concentration of mass

necessary to explain the speed of the

 (20)whirling gas is not necessarily a black

       hole:  the concentration in M87 might

       be a cluster of a billion or so dim stars.

  The same hypothesis might have

been applied to the galaxy NGC 4258,

 (25)but the notion of such a cluster’s

existing in NGC 4258 was severely

undermined when astronomers mea-

sured the speed of a ring of dust and

gas rotating close to the galaxy’s

 (30)center.  From its speed, they calcu-

lated that the core’s density is more

than 40 times the density estimated

      for any other galaxy.  If the center of

NGC 4258 were a star cluster, the

 (35)stars would be so closely spaced

that collisions between individual

stars would have long ago torn the

cluster apart.

Which of the following, if true, would most clearly undermine the possible explanation for the whirling gas in M87 that is mentioned in the last sentence of the first paragraph?

1. The stars in a star cluster at the center of M87 could exert a strong gravitational force without tearing the cluster apart.

2. A cluster of stars at the center would preclude the existence of certain other astronomical phenomena that have been observed at the center of M87.

3. The stars within many existing galaxies, such as NGC 4258, are more closely spaced than are the stars within the core of M87.

4. Only one other galaxy has been observed to contain gas clouds whirling about its center as they do about the core of M87.

5. The gravitational force of a cluster of a billion or so dim stars would be sufficient to cause a whirling ring of gas and dust to collect around the center of a galaxy.

A is correct。  please help...

看了以前的讨论贴，我觉得a.b都不对

应该是 E

The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

问的是两个观点的相同之处：

believe that the large concentration

 (15)of mass at the galaxy’s center is a

black hole whose gravity is causing

the gas to whirl.  A few skeptics have

argued that the concentration of mass

necessary to explain the speed of the

 (20)whirling gas is not necessarily a black

        hole:  the concentration in M87 might

        be a cluster of a billion or so dim stars.

就是说大家都同意有MASS但是一个说是星云，一个说是黑洞。

而A,B只是一方的意见，

发现两个版本的题目不一样，以前的

Q10:

The skeptics mentioned in the first paragraph would be most likely to agree with the astronomers mentioned in line 13 about which of the following statements concerning the galaxy M87?

1. The speed of the gas whirling around the center of M87 is caused by a dense object that is not a black hole.
2. The concentration of mass at the center of M87 is probably a large cluster of dim stars.
3. The presence of a black hole at the center of M87 is the most likely explanation for the speed of the gas whirling about the galaxy’s core.
4. The speed of the gas whirling around the center of M87 is caused by a large concentration of mass at the core of M87.

5. The gravitational influence of a star cluster would not be strong enough to account for the speed of the gas whirling around the core of M87.

我觉得选D,理由同上

我也有同样疑问，Q12为什么选A。

同意楼上 A选项肯定错误！

排除下来还是觉得B比较正确，就是B好像和原文没什么关联。。。

十分同意九楼的说法！

错了赔命。