GWD27-q12没有确定答案, 牛牛给个答案, 方便大家以后的学习

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.

Q12:

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.

Q12:

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.

自己再顶, 等牛人解答

我选的A。。可是为什么答案是B？？？

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

如果没有把星群撕裂，那说明星群的重力还在可以承受的范围内，说明很有可能是星群。所以是加强。

B.       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.

"a black hole forms
when a massive object shrinks catastrophically under its own gravity, leaving
only a gravitational field so strong that nothing escapes it."

说明其他天文现象也无法被观察到的十有八九是黑洞，而不是星群。所以是weaken。

我当时主要preclude不认识，所以没有选出来，不过也觉得这个选项有嫌疑，郁闷，呵呵。

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

无关。如果是less closely也可以是weaken了。

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

无关。只有一个并不能代表M87也不是这种类型。我选了这个，郁闷。

E.       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.

无关。

楼上的，这一句原文没有啊。难道要知道黑洞这个常识么？不可能吧！！

急待NN解答！！！