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　　TWO teams of astronomers using the Hubble Space Telescope and other instruments have found evidence(证据)of a type of black hole that has never been seen before.

　　Roeland Van Der Marel of the Space Telescope Science Institute in Baltimore said last week his group has confirmed(证实) the existence of a midsized black hole in a cluster (group) of stars called M15, about 32,000 light years away.

　　Yan Der Marel said the black hole has about 4,000 times the mass of the sun, which makes it the smallest galactic(银河的)black hole ever found.

　　Another group, led by Michael Rich of the University of California, Los Angeles, looked into a cluster of stars called GI and found a black hole that has about. 20,000 times the mass of the sun. It is some 2.2 million light years away.

　　Using the motion of stars within the clusters, the astronomers could determine the mass of the star groups and of the black holes. They found that the ratio(rate) of the mass of black holes to the mass of globular (球状的) clusters (smaller than a galaxy ) was precisely (精确地) the same as the ratio between supermassive (超质地的) black holes and galaxies. This suggests a neat, uniform(一致的) universal truth that applies the same mass ratio to black holes of all sizes everywhere, explains Karl Gebhardt of the University of Texas, a member of the G1 team.

　　The new discovery may help astronomers answer a basic question: Which came first. galaxies or black holes? Both theories have been proposed and finding intermediatesized(中等规模的) black holes may help answer that question.

1．The astronomers from ________ American institutes and universities discovered the black holes.

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2．Where do the black holes exist?

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A．In a cluster of stars called M15.

B．In a clusters of stars called G1

C．In clusters of stars of the galaxy.

D．Between the sun and the earth.

3．Which of the following is NOT true?

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A．The scientists determined the mass of the black holes using the motion of stars within the clusters.

B．Midsized black holes can give evidence for the answer to“Which came first, galaxies or black holes”.

C．The ratio of the mass of black holes of all sizes is the same.

D．The ratio of the mass between supermassive black holes and galaxies is larger than that between black holes to the mass of globular clusters.

4．Which is the most proper title of the article?

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A．Search for the origin of black holes

B．More black holes are discovered

C．Which came first, galaxies or black holes?

D．Search for more black holes