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.
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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?
Answer:
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Q11:
The passage asserts which of the following about the existence of black holes?
Answer:
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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?
大家帮忙看看12题应该选什么?谢谢!
12题也折磨了我好久。这题考的是逻辑。
第一段最后一句说不一定是黑洞,有可能是因为很多星星组成。要削弱,只要证明是黑洞就行了。根据第二段的内容,很多星星的话,就会tear the cluster apart,但A中说有很大的重力,却without tearing the cluster apart,因此说明不是星星,就有可能是黑洞了。所以削弱。
可是A不是承认了那是星星么,
如果不会tear the cluster apart,就是说星星的存在是可能的,
那就是strengthen了 而不是 undermine了第一段最后一句中 skeptic的说法:
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.
many thanks !!!!!
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